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when merging two loads, make sure to take the min of their alignment,

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not the max.  This didn't matter until the previous patch because
instcombine would refuse to sink loads with differenting alignments.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85738 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2009-11-01 20:07:07 +00:00
parent 751a362c22
commit a664bb7bdc
2 changed files with 27 additions and 1 deletions
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2
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -10774,7 +10774,7 @@ Instruction *InstCombiner::FoldPHIArgLoadIntoPHI(PHINode &PN) {
if ((LoadAlignment != 0) != (LI->getAlignment() != 0))
return 0;
LoadAlignment = std::max(LoadAlignment, LI->getAlignment());
LoadAlignment = std::min(LoadAlignment, LI->getAlignment());
// If the PHI is of volatile loads and the load block has multiple
// successors, sinking it would remove a load of the volatile value from

26
test/Transforms/InstCombine/phi.ll
View File

@ -157,9 +157,35 @@ bb1:
bb2:
%E = phi i32 [ %C, %bb ], [ %D, %bb1 ]
ret i32 %E
; CHECK: @test9
; CHECK: bb2:
; CHECK-NEXT: phi i32* [ %B, %bb ], [ %A, %bb1 ]
; CHECK-NEXT: %E = load i32* %{{[^,]*}}, align 1
; CHECK-NEXT: ret i32 %E
}
define i32 @test10(i32* %A, i32* %B) {
entry:
%c = icmp eq i32* %A, null
br i1 %c, label %bb1, label %bb
bb:
%C = load i32* %B, align 16
br label %bb2
bb1:
%D = load i32* %A, align 32
br label %bb2
bb2:
%E = phi i32 [ %C, %bb ], [ %D, %bb1 ]
ret i32 %E
; CHECK: @test10
; CHECK: bb2:
; CHECK-NEXT: phi i32* [ %B, %bb ], [ %A, %bb1 ]
; CHECK-NEXT: %E = load i32* %{{[^,]*}}, align 16
; CHECK-NEXT: ret i32 %E
}