6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-02-14 02:33:53 +00:00
Code Issues Projects Releases Wiki Activity

Don't do (X != Y) ? X : Y -> X for floating-point values; it doesn't

Browse Source 
handle NaN properly.

Do (X une Y) ? X : Y  -> X if one of X and Y is not zero.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96955 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-02-23 17:17:57 +00:00
parent cf453ee70a
commit 21dc20cbd6
2 changed files with 76 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
lib/Transforms/InstCombine/InstCombineSelect.cpp
View File

@ -539,9 +539,18 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
!CFPf->getValueAPF().isZero()))
return ReplaceInstUsesWith(SI, FalseVal);
}
// Transform (X != Y) ? X : Y -> X
if (FCI->getPredicate() == FCmpInst::FCMP_ONE)
// Transform (X une Y) ? X : Y -> X
if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
// This is not safe in general for floating point:
// consider X== -0, Y== +0.
// It becomes safe if either operand is a nonzero constant.
ConstantFP *CFPt, *CFPf;
if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
!CFPt->getValueAPF().isZero()) ||
((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
!CFPf->getValueAPF().isZero()))
return ReplaceInstUsesWith(SI, TrueVal);
}
// NOTE: if we wanted to, this is where to detect MIN/MAX
} else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){
@ -557,9 +566,18 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
!CFPf->getValueAPF().isZero()))
return ReplaceInstUsesWith(SI, FalseVal);
}
// Transform (X != Y) ? Y : X -> Y
if (FCI->getPredicate() == FCmpInst::FCMP_ONE)
return ReplaceInstUsesWith(SI, TrueVal);
// Transform (X une Y) ? Y : X -> Y
if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
// This is not safe in general for floating point:
// consider X== -0, Y== +0.
// It becomes safe if either operand is a nonzero constant.
ConstantFP *CFPt, *CFPf;
if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
!CFPt->getValueAPF().isZero()) ||
((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
!CFPf->getValueAPF().isZero()))
return ReplaceInstUsesWith(SI, TrueVal);
}
// NOTE: if we wanted to, this is where to detect MIN/MAX
}
// NOTE: if we wanted to, this is where to detect ABS

53
test/Transforms/InstCombine/fcmp-select.ll Normal file
View File

@ -0,0 +1,53 @@
; RUN: opt < %s -instcombine -S | FileCheck %s
; x != y ? x : y -> x if it's the right kind of != and at least
; one of x and y is not negative zero.
; CHECK: f0
; CHECK: ret double %x
define double @f0(double %x) nounwind readnone {
entry:
%cmp = fcmp une double %x, -1.0
%cond = select i1 %cmp, double %x, double -1.0
ret double %cond
}
; CHECK: f1
; CHECK: ret double -1.000000e+00
define double @f1(double %x) nounwind readnone {
entry:
%cmp = fcmp une double %x, -1.0
%cond = select i1 %cmp, double -1.0, double %x
ret double %cond
}
; CHECK: f2
; CHECK: ret double %cond
define double @f2(double %x, double %y) nounwind readnone {
entry:
%cmp = fcmp une double %x, %y
%cond = select i1 %cmp, double %x, double %y
ret double %cond
}
; CHECK: f3
; CHECK: ret double %cond
define double @f3(double %x, double %y) nounwind readnone {
entry:
%cmp = fcmp une double %x, %y
%cond = select i1 %cmp, double %y, double %x
ret double %cond
}
; CHECK: f4
; CHECK: ret double %cond
define double @f4(double %x) nounwind readnone {
entry:
%cmp = fcmp one double %x, -1.0
%cond = select i1 %cmp, double %x, double -1.0
ret double %cond
}
; CHECK: f5
; CHECK: ret double %cond
define double @f5(double %x) nounwind readnone {
entry:
%cmp = fcmp one double %x, -1.0
%cond = select i1 %cmp, double -1.0, double %x
ret double %cond
}