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llvm-mirror/test/CodeGen/Thumb2/2010-02-11-phi-cycle.ll
Guozhi Wei 2be00d9e54 [MBP] Avoid tail duplication if it can't bring benefit
Current tail duplication integrated in bb layout is designed to increase the fallthrough from a BB's predecessor to its successor, but we have observed cases that duplication doesn't increase fallthrough, or it brings too much size overhead.

To overcome these two issues in function canTailDuplicateUnplacedPreds I add two checks:

  make sure there is at least one duplication in current work set.
  the number of duplication should not exceed the number of successors.

The modification in hasBetterLayoutPredecessor fixes a bug that potential predecessor must be at the bottom of a chain.

Differential Revision: https://reviews.llvm.org/D64376
2019-12-06 09:53:53 -08:00

78 lines
3.0 KiB
LLVM

; RUN: llc < %s -mtriple=thumbv7-apple-darwin | FileCheck %s
target datalayout = "e-p:32:32:32-i1:8:32-i8:8:32-i16:16:32-i32:32:32-i64:32:32-f32:32:32-f64:32:32-v64:64:64-v128:128:128-a0:0:32-n32"
define i32 @test(i32 %n) nounwind {
; CHECK-LABEL: test:
; CHECK-NOT: mov
; CHECK: return
entry:
%0 = icmp eq i32 %n, 1 ; <i1> [#uses=1]
br i1 %0, label %return, label %bb.nph
bb.nph: ; preds = %entry
%tmp = add i32 %n, -1 ; <i32> [#uses=1]
br label %bb
bb: ; preds = %bb.nph, %bb
%indvar = phi i32 [ 0, %bb.nph ], [ %indvar.next, %bb ] ; <i32> [#uses=1]
%u.05 = phi i64 [ undef, %bb.nph ], [ %ins, %bb ] ; <i64> [#uses=1]
%1 = tail call i32 @f() nounwind ; <i32> [#uses=1]
%tmp4 = zext i32 %1 to i64 ; <i64> [#uses=1]
%mask = and i64 %u.05, -4294967296 ; <i64> [#uses=1]
%ins = or i64 %tmp4, %mask ; <i64> [#uses=2]
tail call void @g(i64 %ins) nounwind
%indvar.next = add i32 %indvar, 1 ; <i32> [#uses=2]
%exitcond = icmp eq i32 %indvar.next, %tmp ; <i1> [#uses=1]
br i1 %exitcond, label %return, label %bb
return: ; preds = %bb, %entry
ret i32 undef
}
define i32 @test_dead_cycle(i32 %n) nounwind {
; CHECK-LABEL: test_dead_cycle:
; CHECK: subs
; also check for duplicate induction variables (radar 7645034)
; CHECK: subs r{{.*}}, #1
; CHECK-NOT: subs r{{.*}}, #1
; CHECK: bl
; CHECK-NOT: mov
; CHECK: bl
; CHECK: pop
entry:
%0 = icmp eq i32 %n, 1 ; <i1> [#uses=1]
br i1 %0, label %return, label %bb.nph
bb.nph: ; preds = %entry
%tmp = add i32 %n, -1 ; <i32> [#uses=2]
br label %bb
bb: ; preds = %bb.nph, %bb2
%indvar = phi i32 [ 0, %bb.nph ], [ %indvar.next, %bb2 ] ; <i32> [#uses=2]
%u.17 = phi i64 [ undef, %bb.nph ], [ %u.0, %bb2 ] ; <i64> [#uses=2]
%tmp9 = sub i32 %tmp, %indvar ; <i32> [#uses=1]
%1 = icmp sgt i32 %tmp9, 1 ; <i1> [#uses=1]
br i1 %1, label %bb1, label %bb2
bb1: ; preds = %bb
%2 = tail call i32 @f() nounwind ; <i32> [#uses=1]
%tmp6 = zext i32 %2 to i64 ; <i64> [#uses=1]
%mask = and i64 %u.17, -4294967296 ; <i64> [#uses=1]
%ins = or i64 %tmp6, %mask ; <i64> [#uses=1]
tail call void @g(i64 %ins) nounwind
br label %bb2
bb2: ; preds = %bb1, %bb
%u.0 = phi i64 [ %ins, %bb1 ], [ %u.17, %bb ] ; <i64> [#uses=2]
%indvar.next = add i32 %indvar, 1 ; <i32> [#uses=2]
%exitcond = icmp eq i32 %indvar.next, %tmp ; <i1> [#uses=1]
br i1 %exitcond, label %return, label %bb
return: ; preds = %bb2, %entry
ret i32 undef
}
declare i32 @f()
declare void @g(i64)