[llvm] r323343 - InstSimplify: If divisor element is undef simplify to undef
Zvi Rackover via llvm-commits
llvm-commits at lists.llvm.org
Wed Jan 24 09:22:00 PST 2018
Author: zvi
Date: Wed Jan 24 09:22:00 2018
New Revision: 323343
URL: http://llvm.org/viewvc/llvm-project?rev=323343&view=rev
Log:
InstSimplify: If divisor element is undef simplify to undef
Summary:
If any vector divisor element is undef, we can arbitrarily choose it be
zero which would make the div/rem an undef value by definition.
Reviewers: spatel, reames
Reviewed By: spatel
Subscribers: magabari, llvm-commits
Differential Revision: https://reviews.llvm.org/D42485
Modified:
llvm/trunk/lib/Analysis/InstructionSimplify.cpp
llvm/trunk/test/Transforms/InstSimplify/div.ll
llvm/trunk/test/Transforms/InstSimplify/rem.ll
Modified: llvm/trunk/lib/Analysis/InstructionSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/InstructionSimplify.cpp?rev=323343&r1=323342&r2=323343&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/InstructionSimplify.cpp (original)
+++ llvm/trunk/lib/Analysis/InstructionSimplify.cpp Wed Jan 24 09:22:00 2018
@@ -868,13 +868,14 @@ static Value *simplifyDivRem(Value *Op0,
if (match(Op1, m_Zero()))
return UndefValue::get(Ty);
- // If any element of a constant divisor vector is zero, the whole op is undef.
+ // If any element of a constant divisor vector is zero or undef, the whole op
+ // is undef.
auto *Op1C = dyn_cast<Constant>(Op1);
if (Op1C && Ty->isVectorTy()) {
unsigned NumElts = Ty->getVectorNumElements();
for (unsigned i = 0; i != NumElts; ++i) {
Constant *Elt = Op1C->getAggregateElement(i);
- if (Elt && Elt->isNullValue())
+ if (Elt && (Elt->isNullValue() || isa<UndefValue>(Elt)))
return UndefValue::get(Ty);
}
}
Modified: llvm/trunk/test/Transforms/InstSimplify/div.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstSimplify/div.ll?rev=323343&r1=323342&r2=323343&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstSimplify/div.ll (original)
+++ llvm/trunk/test/Transforms/InstSimplify/div.ll Wed Jan 24 09:22:00 2018
@@ -34,6 +34,22 @@ define <2 x i8> @udiv_zero_elt_vec(<2 x
ret <2 x i8> %div
}
+define <2 x i8> @sdiv_undef_elt_vec(<2 x i8> %x) {
+; CHECK-LABEL: @sdiv_undef_elt_vec(
+; CHECK-NEXT: ret <2 x i8> undef
+;
+ %div = sdiv <2 x i8> %x, <i8 -42, i8 undef>
+ ret <2 x i8> %div
+}
+
+define <2 x i8> @udiv_undef_elt_vec(<2 x i8> %x) {
+; CHECK-LABEL: @udiv_undef_elt_vec(
+; CHECK-NEXT: ret <2 x i8> undef
+;
+ %div = udiv <2 x i8> %x, <i8 undef, i8 42>
+ ret <2 x i8> %div
+}
+
; Division-by-zero is undef. UB in any vector lane means the whole op is undef.
; Thus, we can simplify this: if any element of 'y' is 0, we can do anything.
; Therefore, assume that all elements of 'y' must be 1.
Modified: llvm/trunk/test/Transforms/InstSimplify/rem.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstSimplify/rem.ll?rev=323343&r1=323342&r2=323343&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstSimplify/rem.ll (original)
+++ llvm/trunk/test/Transforms/InstSimplify/rem.ll Wed Jan 24 09:22:00 2018
@@ -35,6 +35,22 @@ define <2 x i8> @urem_zero_elt_vec(<2 x
ret <2 x i8> %rem
}
+define <2 x i8> @srem_undef_elt_vec(<2 x i8> %x) {
+; CHECK-LABEL: @srem_undef_elt_vec(
+; CHECK-NEXT: ret <2 x i8> undef
+;
+ %rem = srem <2 x i8> %x, <i8 -42, i8 undef>
+ ret <2 x i8> %rem
+}
+
+define <2 x i8> @urem_undef_elt_vec(<2 x i8> %x) {
+; CHECK-LABEL: @urem_undef_elt_vec(
+; CHECK-NEXT: ret <2 x i8> undef
+;
+ %rem = urem <2 x i8> %x, <i8 undef, i8 42>
+ ret <2 x i8> %rem
+}
+
; Division-by-zero is undef. UB in any vector lane means the whole op is undef.
; Thus, we can simplify this: if any element of 'y' is 0, we can do anything.
; Therefore, assume that all elements of 'y' must be 1.
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