maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

Revert r170020, "Simplify negated bit test", for now. 

This assumes (1 << n) is always not zero. Consider n is greater than word size.
Although I know it is undefined, this transforms undefined behavior hidden.

This led clang unexpected behavior with some failures. I will investigate to fix undefined shl in clang.

llvm-svn: 170128
This commit is contained in:
NAKAMURA Takumi 2012-12-13 14:28:16 +00:00
parent 18ec81b854
commit 38d2b2442f
2 changed files with 0 additions and 44 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -2034,15 +2034,6 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
CI->countTrailingZeros()));
}
// Turn x&~y == 0 into x&y != 0 if x is a power of 2.
Value *X = 0, *Y = 0;
if (match(Op0, m_And(m_Value(X), m_Not(m_Value(Y)))) &&
match(Op1, m_Zero()) && isKnownToBeAPowerOfTwo(X, TD)) {
return new ICmpInst(ICmpInst::ICMP_NE,
Builder->CreateAnd(X, Y),
Op1);
}
break;
}
case ICmpInst::ICMP_NE: {
@ -2080,15 +2071,6 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
CI->countTrailingZeros()));
}
// Turn x&~y != 0 into x&y == 0 if x is a power of 2.
Value *X = 0, *Y = 0;
if (match(Op0, m_And(m_Value(X), m_Not(m_Value(Y)))) &&
match(Op1, m_Zero()) && isKnownToBeAPowerOfTwo(X, TD)) {
return new ICmpInst(ICmpInst::ICMP_EQ,
Builder->CreateAnd(X, Y),
Op1);
}
break;
}
case ICmpInst::ICMP_ULT:

26
llvm/test/Transforms/InstCombine/icmp.ll
View File

@ -677,29 +677,3 @@ define i1 @test66(i64 %A, i64 %B) {
; CHECK-NEXT: ret i1 true
ret i1 %cmp
}
define i1 @test67(i32 %A, i32 %B) {
%neg = xor i32 %A, -1
%shl = shl i32 1, %B
%and = and i32 %shl, %neg
%cmp = icmp ne i32 %and, 0
; CHECK: @test67
; CHECK-NEXT: %shl = shl i32 1, %B
; CHECK-NEXT: %1 = and i32 %shl, %A
; CHECK-NEXT: %cmp = icmp eq i32 %1, 0
; CHECK-NEXT: ret i1 %cmp
ret i1 %cmp
}
define i1 @test68(i32 %A, i32 %B) {
%neg = xor i32 %A, -1
%shl = shl i32 1, %B
%and = and i32 %shl, %neg
%cmp = icmp eq i32 %and, 0
; CHECK: @test68
; CHECK-NEXT: %shl = shl i32 1, %B
; CHECK-NEXT: %1 = and i32 %shl, %A
; CHECK-NEXT: %cmp = icmp ne i32 %1, 0
; CHECK-NEXT: ret i1 %cmp
ret i1 %cmp
}