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llvm-mirror/test/Analysis/ScalarEvolution/nsw-offset.ll
Nikita Popov 318f4a3446 [SCEV] Fix nsw flags for GEP expressions
The SCEV code for constructing GEP expressions currently assumes
that the addition of the base and all the offsets is nsw if the GEP
is inbounds. While the addition of the offsets is indeed nsw, the
addition to the base address is not, as the base address is
interpreted as an unsigned value.

Fix the GEP expression code to not assume nsw for the base+offset
calculation. However, do assume nuw if we know that the offset is
non-negative. With this, we use the same behavior as the
construction of GEP addrecs does. (Modulo the fact that we
disregard SCEV unification, as the pre-existing FIXME points out).

Differential Revision: https://reviews.llvm.org/D90648
2020-11-13 18:19:32 +01:00

79 lines
3.4 KiB
LLVM

; RUN: opt < %s -S -analyze -enable-new-pm=0 -scalar-evolution | FileCheck %s
; RUN: opt < %s -S -disable-output "-passes=print<scalar-evolution>" 2>&1 | FileCheck %s
; ScalarEvolution should be able to fold away the sign-extensions
; on this loop with a primary induction variable incremented with
; a nsw add of 2.
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
define void @foo(i32 %no, double* nocapture %d, double* nocapture %q) nounwind {
entry:
%n = and i32 %no, 4294967294
%0 = icmp sgt i32 %n, 0 ; <i1> [#uses=1]
br i1 %0, label %bb.nph, label %return
bb.nph: ; preds = %entry
br label %bb
bb: ; preds = %bb.nph, %bb1
%i.01 = phi i32 [ %16, %bb1 ], [ 0, %bb.nph ] ; <i32> [#uses=5]
; CHECK: %1 = sext i32 %i.01 to i64
; CHECK: --> {0,+,2}<nuw><nsw><%bb>
%1 = sext i32 %i.01 to i64 ; <i64> [#uses=1]
; CHECK: %2 = getelementptr inbounds double, double* %d, i64 %1
; CHECK: --> {%d,+,16}<nuw><%bb>
%2 = getelementptr inbounds double, double* %d, i64 %1 ; <double*> [#uses=1]
%3 = load double, double* %2, align 8 ; <double> [#uses=1]
%4 = sext i32 %i.01 to i64 ; <i64> [#uses=1]
%5 = getelementptr inbounds double, double* %q, i64 %4 ; <double*> [#uses=1]
%6 = load double, double* %5, align 8 ; <double> [#uses=1]
%7 = or i32 %i.01, 1 ; <i32> [#uses=1]
; CHECK: %8 = sext i32 %7 to i64
; CHECK: --> {1,+,2}<nuw><nsw><%bb>
%8 = sext i32 %7 to i64 ; <i64> [#uses=1]
; CHECK: %9 = getelementptr inbounds double, double* %q, i64 %8
; CHECK: {(8 + %q)<nuw>,+,16}<nuw><%bb>
%9 = getelementptr inbounds double, double* %q, i64 %8 ; <double*> [#uses=1]
; Artificially repeat the above three instructions, this time using
; add nsw instead of or.
%t7 = add nsw i32 %i.01, 1 ; <i32> [#uses=1]
; CHECK: %t8 = sext i32 %t7 to i64
; CHECK: --> {1,+,2}<nuw><nsw><%bb>
%t8 = sext i32 %t7 to i64 ; <i64> [#uses=1]
; CHECK: %t9 = getelementptr inbounds double, double* %q, i64 %t8
; CHECK: {(8 + %q)<nuw>,+,16}<nuw><%bb>
%t9 = getelementptr inbounds double, double* %q, i64 %t8 ; <double*> [#uses=1]
%10 = load double, double* %9, align 8 ; <double> [#uses=1]
%11 = fadd double %6, %10 ; <double> [#uses=1]
%12 = fadd double %11, 3.200000e+00 ; <double> [#uses=1]
%13 = fmul double %3, %12 ; <double> [#uses=1]
%14 = sext i32 %i.01 to i64 ; <i64> [#uses=1]
%15 = getelementptr inbounds double, double* %d, i64 %14 ; <double*> [#uses=1]
store double %13, double* %15, align 8
%16 = add nsw i32 %i.01, 2 ; <i32> [#uses=2]
br label %bb1
bb1: ; preds = %bb
%17 = icmp slt i32 %16, %n ; <i1> [#uses=1]
br i1 %17, label %bb, label %bb1.return_crit_edge
bb1.return_crit_edge: ; preds = %bb1
br label %return
return: ; preds = %bb1.return_crit_edge, %entry
ret void
}
; CHECK: Loop %bb: backedge-taken count is ((-1 + (2 * (%no /u 2))<nuw>) /u 2)
; CHECK: Loop %bb: max backedge-taken count is 1073741822