6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-02-27 02:31:09 +00:00
Code Issues Projects Releases Wiki Activity

only propagate equality comparisons of FP values that we are certain are non-zero

Browse Source 
This is a follow-on to r227491 which tightens the check for propagating FP
values. If a non-constant value happens to be a zero, we would hit the same
bug as before.

Bug noted and patch suggested by Eli Friedman.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230564 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjay Patel 2015-02-25 22:46:08 +00:00
parent 5674975c5e
commit 8e3ef7f186
2 changed files with 50 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
lib/Transforms/Scalar/GVN.cpp
View File

@ -2182,12 +2182,16 @@ bool GVN::propagateEquality(Value *LHS, Value *RHS,
// Handle the floating point versions of equality comparisons too.
if ((isKnownTrue && Cmp->getPredicate() == CmpInst::FCMP_OEQ) ||
(isKnownFalse && Cmp->getPredicate() == CmpInst::FCMP_UNE)) {
// Floating point -0.0 and 0.0 compare equal, so we can't
// propagate a constant based on that comparison.
// Floating point -0.0 and 0.0 compare equal, so we can only
// propagate values if we know that we have a constant and that
// its value is non-zero.
// FIXME: We should do this optimization if 'no signed zeros' is
// applicable via an instruction-level fast-math-flag or some other
// indicator that relaxed FP semantics are being used.
if (!isa<ConstantFP>(Op1) || !cast<ConstantFP>(Op1)->isZero())
if (isa<ConstantFP>(Op1) && !cast<ConstantFP>(Op1)->isZero())
Worklist.push_back(std::make_pair(Op0, Op1));
}

47
test/Transforms/GVN/edge.ll
View File

@ -59,7 +59,7 @@ bb2:
ret void
}
define double @fcmp_oeq(double %x, double %y) {
define double @fcmp_oeq_not_zero(double %x, double %y) {
entry:
%cmp = fcmp oeq double %y, 2.0
br i1 %cmp, label %if, label %return
@ -72,11 +72,11 @@ return:
%retval = phi double [ %div, %if ], [ %x, %entry ]
ret double %retval
; CHECK-LABEL: define double @fcmp_oeq(
; CHECK-LABEL: define double @fcmp_oeq_not_zero(
; CHECK: %div = fdiv double %x, 2.0
}
define double @fcmp_une(double %x, double %y) {
define double @fcmp_une_not_zero(double %x, double %y) {
entry:
%cmp = fcmp une double %y, 2.0
br i1 %cmp, label %return, label %else
@ -89,7 +89,7 @@ return:
%retval = phi double [ %div, %else ], [ %x, %entry ]
ret double %retval
; CHECK-LABEL: define double @fcmp_une(
; CHECK-LABEL: define double @fcmp_une_not_zero(
; CHECK: %div = fdiv double %x, 2.0
}
@ -129,3 +129,42 @@ return:
; CHECK-LABEL: define double @fcmp_une_zero(
; CHECK: %div = fdiv double %x, %y
}
; We also cannot propagate a value if it's not a constant.
; This is because the value could be 0.0 or -0.0.
define double @fcmp_oeq_maybe_zero(double %x, double %y, double %z1, double %z2) {
entry:
%z = fadd double %z1, %z2
%cmp = fcmp oeq double %y, %z
br i1 %cmp, label %if, label %return
if:
%div = fdiv double %x, %z
br label %return
return:
%retval = phi double [ %div, %if ], [ %x, %entry ]
ret double %retval
; CHECK-LABEL: define double @fcmp_oeq_maybe_zero(
; CHECK: %div = fdiv double %x, %z
}
define double @fcmp_une_maybe_zero(double %x, double %y, double %z1, double %z2) {
entry:
%z = fadd double %z1, %z2
%cmp = fcmp une double %y, %z
br i1 %cmp, label %return, label %else
else:
%div = fdiv double %x, %z
br label %return
return:
%retval = phi double [ %div, %else ], [ %x, %entry ]
ret double %retval
; CHECK-LABEL: define double @fcmp_une_maybe_zero(
; CHECK: %div = fdiv double %x, %z
}