summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorDavid Majnemer <david.majnemer@gmail.com>2014-05-14 20:16:28 +0000
committerDavid Majnemer <david.majnemer@gmail.com>2014-05-14 20:16:28 +0000
commitcd237ed5853bda1dab27323236119e4342a19860 (patch)
treeae30d37e6dbf9018ec09943c2628b04a3c861973
parente0776de2df9c47af5002cbc04354b52f3a1ee9b3 (diff)
InstSimplify: Optimize signed icmp of -(zext V)
Summary: We know that -(zext V) will always be <= zero, simplify signed icmps that have these. Uncovered using http://www.cs.utah.edu/~regehr/souper/ Reviewers: nicholas Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D3754 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208809 91177308-0d34-0410-b5e6-96231b3b80d8
-rw-r--r--lib/Analysis/InstructionSimplify.cpp22
-rw-r--r--test/Transforms/InstSimplify/compare.ll60
2 files changed, 82 insertions, 0 deletions
diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index 4c621b0e911..5421a399226 100644
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -2280,6 +2280,28 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
}
}
+ // 0 - (zext X) pred C
+ if (!CmpInst::isUnsigned(Pred) && match(LHS, m_Neg(m_ZExt(m_Value())))) {
+ if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) {
+ if (RHSC->getValue().isStrictlyPositive()) {
+ if (Pred == ICmpInst::ICMP_SLT)
+ return ConstantInt::getTrue(RHSC->getContext());
+ if (Pred == ICmpInst::ICMP_SGE)
+ return ConstantInt::getFalse(RHSC->getContext());
+ if (Pred == ICmpInst::ICMP_EQ)
+ return ConstantInt::getFalse(RHSC->getContext());
+ if (Pred == ICmpInst::ICMP_NE)
+ return ConstantInt::getTrue(RHSC->getContext());
+ }
+ if (RHSC->getValue().isNonNegative()) {
+ if (Pred == ICmpInst::ICMP_SLE)
+ return ConstantInt::getTrue(RHSC->getContext());
+ if (Pred == ICmpInst::ICMP_SGT)
+ return ConstantInt::getFalse(RHSC->getContext());
+ }
+ }
+ }
+
// icmp pred (urem X, Y), Y
if (LBO && match(LBO, m_URem(m_Value(), m_Specific(RHS)))) {
bool KnownNonNegative, KnownNegative;
diff --git a/test/Transforms/InstSimplify/compare.ll b/test/Transforms/InstSimplify/compare.ll
index ee6be0458cb..76cff902c96 100644
--- a/test/Transforms/InstSimplify/compare.ll
+++ b/test/Transforms/InstSimplify/compare.ll
@@ -757,3 +757,63 @@ define <4 x i8> @vectorselectfold2(<4 x i8> %a, <4 x i8> %b) {
; CHECK-LABEL: @vectorselectfold
; CHECK-NEXT: ret <4 x i8> %a
}
+
+define i1 @compare_always_true_slt(i16 %a) {
+ %1 = zext i16 %a to i32
+ %2 = sub nsw i32 0, %1
+ %3 = icmp slt i32 %2, 1
+ ret i1 %3
+
+; CHECK-LABEL: @compare_always_true_slt
+; CHECK-NEXT: ret i1 true
+}
+
+define i1 @compare_always_true_sle(i16 %a) {
+ %1 = zext i16 %a to i32
+ %2 = sub nsw i32 0, %1
+ %3 = icmp sle i32 %2, 0
+ ret i1 %3
+
+; CHECK-LABEL: @compare_always_true_sle
+; CHECK-NEXT: ret i1 true
+}
+
+define i1 @compare_always_false_sgt(i16 %a) {
+ %1 = zext i16 %a to i32
+ %2 = sub nsw i32 0, %1
+ %3 = icmp sgt i32 %2, 0
+ ret i1 %3
+
+; CHECK-LABEL: @compare_always_false_sgt
+; CHECK-NEXT: ret i1 false
+}
+
+define i1 @compare_always_false_sge(i16 %a) {
+ %1 = zext i16 %a to i32
+ %2 = sub nsw i32 0, %1
+ %3 = icmp sge i32 %2, 1
+ ret i1 %3
+
+; CHECK-LABEL: @compare_always_false_sge
+; CHECK-NEXT: ret i1 false
+}
+
+define i1 @compare_always_false_eq(i16 %a) {
+ %1 = zext i16 %a to i32
+ %2 = sub nsw i32 0, %1
+ %3 = icmp eq i32 %2, 1
+ ret i1 %3
+
+; CHECK-LABEL: @compare_always_false_eq
+; CHECK-NEXT: ret i1 false
+}
+
+define i1 @compare_always_false_ne(i16 %a) {
+ %1 = zext i16 %a to i32
+ %2 = sub nsw i32 0, %1
+ %3 = icmp ne i32 %2, 1
+ ret i1 %3
+
+; CHECK-LABEL: @compare_always_false_ne
+; CHECK-NEXT: ret i1 true
+}