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4e5297ed76
When LSR processes code like
int accumulator = 0;
for (int i = 0; i < N; i++) {
accummulator += i;
use((double) accummulator);
}
It may decide to replace integer `accumulator` with a double Shadow IV to get rid
of casts. The problem with that is that the `accumulator`'s value may overflow.
Starting from this moment, the behavior of integer and double accumulators
will differ.
This patch strenghtens up the conditions of Shadow IV mechanism applicability.
We only allow it for IVs that are proved to be `AddRec`s with `nsw`/`nuw` flag.
Differential Revision: https://reviews.llvm.org/D37209
llvm-svn: 311986
216 lines
6.0 KiB
LLVM
216 lines
6.0 KiB
LLVM
; RUN: opt < %s -loop-reduce -S -mtriple=x86_64-unknown-unknown 2>&1 | FileCheck %s
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; Provide legal integer types.
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target datalayout = "n8:16:32:64"
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define void @foobar(i32 %n) nounwind {
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; CHECK-LABEL: foobar(
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; CHECK: phi double
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entry:
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%cond = icmp eq i32 %n, 0 ; <i1>:0 [#uses=2]
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br i1 %cond, label %return, label %bb.nph
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bb.nph: ; preds = %entry
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%umax = select i1 %cond, i32 1, i32 %n ; <i32> [#uses=1]
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br label %bb
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bb: ; preds = %bb, %bb.nph
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%i.03 = phi i32 [ 0, %bb.nph ], [ %indvar.next, %bb ] ; <i32> [#uses=3]
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tail call void @bar( i32 %i.03 ) nounwind
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%tmp1 = uitofp i32 %i.03 to double ; <double>:1 [#uses=1]
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tail call void @foo( double %tmp1 ) nounwind
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%indvar.next = add nsw nuw i32 %i.03, 1 ; <i32> [#uses=2]
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%exitcond = icmp eq i32 %indvar.next, %umax ; <i1> [#uses=1]
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br i1 %exitcond, label %return, label %bb
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return: ; preds = %bb, %entry
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ret void
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}
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; Unable to eliminate cast because the mantissa bits for double are not enough
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; to hold all of i64 IV bits.
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define void @foobar2(i64 %n) nounwind {
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; CHECK-LABEL: foobar2(
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; CHECK-NOT: phi double
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; CHECK-NOT: phi float
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entry:
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%cond = icmp eq i64 %n, 0 ; <i1>:0 [#uses=2]
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br i1 %cond, label %return, label %bb.nph
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bb.nph: ; preds = %entry
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%umax = select i1 %cond, i64 1, i64 %n ; <i64> [#uses=1]
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br label %bb
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bb: ; preds = %bb, %bb.nph
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%i.03 = phi i64 [ 0, %bb.nph ], [ %indvar.next, %bb ] ; <i64> [#uses=3]
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%tmp1 = trunc i64 %i.03 to i32 ; <i32>:1 [#uses=1]
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tail call void @bar( i32 %tmp1 ) nounwind
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%tmp2 = uitofp i64 %i.03 to double ; <double>:2 [#uses=1]
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tail call void @foo( double %tmp2 ) nounwind
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%indvar.next = add nsw nuw i64 %i.03, 1 ; <i64> [#uses=2]
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%exitcond = icmp eq i64 %indvar.next, %umax ; <i1> [#uses=1]
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br i1 %exitcond, label %return, label %bb
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return: ; preds = %bb, %entry
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ret void
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}
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; Unable to eliminate cast due to potentional overflow.
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define void @foobar3() nounwind {
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; CHECK-LABEL: foobar3(
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; CHECK-NOT: phi double
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; CHECK-NOT: phi float
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entry:
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%tmp0 = tail call i32 (...) @nn( ) nounwind ; <i32>:0 [#uses=1]
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%cond = icmp eq i32 %tmp0, 0 ; <i1>:1 [#uses=1]
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br i1 %cond, label %return, label %bb
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bb: ; preds = %bb, %entry
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%i.03 = phi i32 [ 0, %entry ], [ %indvar.next, %bb ] ; <i32> [#uses=3]
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tail call void @bar( i32 %i.03 ) nounwind
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%tmp2 = uitofp i32 %i.03 to double ; <double>:2 [#uses=1]
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tail call void @foo( double %tmp2 ) nounwind
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%indvar.next = add nuw nsw i32 %i.03, 1 ; <i32>:3 [#uses=2]
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%tmp4 = tail call i32 (...) @nn( ) nounwind ; <i32>:4 [#uses=1]
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%exitcond = icmp ugt i32 %tmp4, %indvar.next ; <i1>:5 [#uses=1]
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br i1 %exitcond, label %bb, label %return
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return: ; preds = %bb, %entry
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ret void
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}
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; Unable to eliminate cast due to overflow.
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define void @foobar4() nounwind {
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; CHECK-LABEL: foobar4(
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; CHECK-NOT: phi double
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; CHECK-NOT: phi float
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entry:
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br label %bb.nph
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bb.nph: ; preds = %entry
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br label %bb
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bb: ; preds = %bb, %bb.nph
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%i.03 = phi i8 [ 0, %bb.nph ], [ %indvar.next, %bb ] ; <i32> [#uses=3]
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%tmp2 = sext i8 %i.03 to i32 ; <i32>:0 [#uses=1]
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tail call void @bar( i32 %tmp2 ) nounwind
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%tmp3 = uitofp i8 %i.03 to double ; <double>:1 [#uses=1]
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tail call void @foo( double %tmp3 ) nounwind
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%indvar.next = add nsw nuw i8 %i.03, 1 ; <i32> [#uses=2]
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%tmp = sext i8 %indvar.next to i32
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%exitcond = icmp eq i32 %tmp, 32767 ; <i1> [#uses=1]
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br i1 %exitcond, label %return, label %bb
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return: ; preds = %bb, %entry
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ret void
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}
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; Unable to eliminate cast because the integer IV overflows (accum exceeds
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; SINT_MAX).
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define i32 @foobar5() {
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; CHECK-LABEL: foobar5(
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; CHECK-NOT: phi double
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; CHECK-NOT: phi float
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entry:
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br label %loop
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loop:
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%accum = phi i32 [ -3220, %entry ], [ %accum.next, %loop ]
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%iv = phi i32 [ 12, %entry ], [ %iv.next, %loop ]
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%tmp1 = sitofp i32 %accum to double
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tail call void @foo( double %tmp1 ) nounwind
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%accum.next = add i32 %accum, 9597741
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%iv.next = add nuw nsw i32 %iv, 1
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%exitcond = icmp ugt i32 %iv, 235
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br i1 %exitcond, label %exit, label %loop
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exit: ; preds = %loop
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ret i32 %accum.next
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}
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; Can eliminate if we set nsw and, thus, think that we don't overflow SINT_MAX.
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define i32 @foobar6() {
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; CHECK-LABEL: foobar6(
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; CHECK: phi double
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entry:
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br label %loop
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loop:
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%accum = phi i32 [ -3220, %entry ], [ %accum.next, %loop ]
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%iv = phi i32 [ 12, %entry ], [ %iv.next, %loop ]
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%tmp1 = sitofp i32 %accum to double
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tail call void @foo( double %tmp1 ) nounwind
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%accum.next = add nsw i32 %accum, 9597741
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%iv.next = add nuw nsw i32 %iv, 1
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%exitcond = icmp ugt i32 %iv, 235
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br i1 %exitcond, label %exit, label %loop
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exit: ; preds = %loop
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ret i32 %accum.next
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}
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; Unable to eliminate cast because the integer IV overflows (accum exceeds
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; UINT_MAX).
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define i32 @foobar7() {
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; CHECK-LABEL: foobar7(
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; CHECK-NOT: phi double
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; CHECK-NOT: phi float
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entry:
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br label %loop
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loop:
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%accum = phi i32 [ -3220, %entry ], [ %accum.next, %loop ]
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%iv = phi i32 [ 12, %entry ], [ %iv.next, %loop ]
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%tmp1 = uitofp i32 %accum to double
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tail call void @foo( double %tmp1 ) nounwind
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%accum.next = add i32 %accum, 9597741
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%iv.next = add nuw nsw i32 %iv, 1
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%exitcond = icmp ugt i32 %iv, 235
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br i1 %exitcond, label %exit, label %loop
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exit: ; preds = %loop
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ret i32 %accum.next
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}
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; Can eliminate if we set nuw and, thus, think that we don't overflow UINT_MAX.
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define i32 @foobar8() {
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; CHECK-LABEL: foobar8(
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; CHECK: phi double
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entry:
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br label %loop
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loop:
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%accum = phi i32 [ -3220, %entry ], [ %accum.next, %loop ]
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%iv = phi i32 [ 12, %entry ], [ %iv.next, %loop ]
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%tmp1 = uitofp i32 %accum to double
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tail call void @foo( double %tmp1 ) nounwind
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%accum.next = add nuw i32 %accum, 9597741
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%iv.next = add nuw nsw i32 %iv, 1
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%exitcond = icmp ugt i32 %iv, 235
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br i1 %exitcond, label %exit, label %loop
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exit: ; preds = %loop
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ret i32 %accum.next
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}
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declare void @bar(i32)
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declare void @foo(double)
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declare i32 @nn(...)
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