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

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

llvm-svn: 85738
This commit is contained in:
Chris Lattner 2009-11-01 20:07:07 +00:00
parent 2a249e267a
commit 328ef89bd1
2 changed files with 27 additions and 1 deletions
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2
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -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
llvm/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
}