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author | Tom Stellard <thomas.stellard@amd.com> | 2015-05-05 14:43:00 +0000 |
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committer | Tom Stellard <thomas.stellard@amd.com> | 2015-05-05 14:43:00 +0000 |
commit | 0ee768621b2f5c1ece736c42a9a32e29083f35ee (patch) | |
tree | d41180fb95570a41d1074c94bfc8ce94a7ebce50 | |
parent | b5344bfff41583c00026e321d6831d4e8790b309 (diff) | |
download | llvm-0ee768621b2f5c1ece736c42a9a32e29083f35ee.tar.gz |
Merging r230564:
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r230564 | spatel | 2015-02-25 17:46:08 -0500 (Wed, 25 Feb 2015) | 8 lines
only propagate equality comparisons of FP values that we are certain are non-zero
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.
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_36@236499 91177308-0d34-0410-b5e6-96231b3b80d8
-rw-r--r-- | lib/Transforms/Scalar/GVN.cpp | 10 | ||||
-rw-r--r-- | test/Transforms/GVN/edge.ll | 47 |
2 files changed, 50 insertions, 7 deletions
diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp index ac13eebf8275..1ed14d001093 100644 --- a/lib/Transforms/Scalar/GVN.cpp +++ b/lib/Transforms/Scalar/GVN.cpp @@ -2183,12 +2183,16 @@ 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)); } diff --git a/test/Transforms/GVN/edge.ll b/test/Transforms/GVN/edge.ll index f28a76bb42d6..0c1a3fbec528 100644 --- a/test/Transforms/GVN/edge.ll +++ b/test/Transforms/GVN/edge.ll @@ -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 +} |