6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-07-22 09:29:31 +00:00
Code Issues Projects Releases Wiki Activity

Fix PR14361: wrong simplification of A+B==B+A. You may think that the old logic

Browse Source 
replaced by this patch is equivalent to the new logic, but you'd be wrong, and
that's exactly where the bug was.  There's a similar bug in instsimplify which
manifests itself as instsimplify failing to simplify this, rather than doing it
wrong, see next commit.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168181 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands 2012-11-16 18:55:49 +00:00
parent 661dfdc9b7
commit afe4539f8e
2 changed files with 32 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -2356,8 +2356,20 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
// Try not to increase register pressure.
BO0->hasOneUse() && BO1->hasOneUse()) {
// Determine Y and Z in the form icmp (X+Y), (X+Z).
Value *Y = (A == C || A == D) ? B : A;
Value *Z = (C == A || C == B) ? D : C;
Value *Y, *Z;
if (A == C) {
Y = B;
Z = D;
} else if (A == D) {
Y = B;
Z = C;
} else if (B == C) {
Y = A;
Z = D;
} else if (B == D) {
Y = A;
Z = C;
}
return new ICmpInst(Pred, Y, Z);
}

18
test/Transforms/InstCombine/icmp.ll
View File

@ -659,3 +659,21 @@ define i1 @test64(i8 %a, i32 %b) nounwind {
; CHECK-NEXT: %c = icmp eq i8 %1, %a
; CHECK-NEXT: ret i1 %c
}
define i1 @test65(i64 %A, i64 %B) {
%s1 = add i64 %A, %B
%s2 = add i64 %A, %B
%cmp = icmp eq i64 %s1, %s2
; CHECK: @test65
; CHECK-NEXT: ret i1 true
ret i1 %cmp
}
define i1 @test66(i64 %A, i64 %B) {
%s1 = add i64 %A, %B
%s2 = add i64 %B, %A
%cmp = icmp eq i64 %s1, %s2
; CHECK: @test66
; CHECK-NEXT: ret i1 true
ret i1 %cmp
}