Handle some more combinations of extend and icmp. Fixes PR1940.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46431 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/llvm/Instructions.h b/include/llvm/Instructions.h
index 76190f1..49ec4f5 100644
--- a/include/llvm/Instructions.h
+++ b/include/llvm/Instructions.h
@@ -642,6 +642,18 @@
/// @brief Return the signed version of the predicate.
static Predicate getSignedPredicate(Predicate pred);
+ /// For example, EQ->EQ, SLE->ULE, UGT->UGT, etc.
+ /// @returns the predicate that would be the result if the operand were
+ /// regarded as unsigned.
+ /// @brief Return the unsigned version of the predicate
+ Predicate getUnsignedPredicate() const {
+ return getUnsignedPredicate(getPredicate());
+ }
+
+ /// This is a static version that you can use without an instruction.
+ /// @brief Return the unsigned version of the predicate.
+ static Predicate getUnsignedPredicate(Predicate pred);
+
/// isEquality - Return true if this predicate is either EQ or NE. This also
/// tests for commutativity.
static bool isEquality(Predicate P) {
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 5ba4857..e56b559 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -5820,18 +5820,22 @@
if (RHSCIOp->getType() != LHSCIOp->getType())
return 0;
- // If the signedness of the two compares doesn't agree (i.e. one is a sext
+ // If the signedness of the two casts doesn't agree (i.e. one is a sext
// and the other is a zext), then we can't handle this.
if (CI->getOpcode() != LHSCI->getOpcode())
return 0;
- // Likewise, if the signedness of the [sz]exts and the compare don't match,
- // then we can't handle this.
- if (isSignedExt != isSignedCmp && !ICI.isEquality())
- return 0;
-
- // Okay, just insert a compare of the reduced operands now!
- return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSCIOp);
+ // Deal with equality cases early.
+ if (ICI.isEquality())
+ return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSCIOp);
+
+ // A signed comparison of sign extended values simplifies into a
+ // signed comparison.
+ if (isSignedCmp && isSignedExt)
+ return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSCIOp);
+
+ // The other three cases all fold into an unsigned comparison.
+ return new ICmpInst(ICI.getUnsignedPredicate(), LHSCIOp, RHSCIOp);
}
// If we aren't dealing with a constant on the RHS, exit early
diff --git a/lib/VMCore/Instructions.cpp b/lib/VMCore/Instructions.cpp
index 156eff1..b945a5a 100644
--- a/lib/VMCore/Instructions.cpp
+++ b/lib/VMCore/Instructions.cpp
@@ -2429,6 +2429,19 @@
}
}
+ICmpInst::Predicate ICmpInst::getUnsignedPredicate(Predicate pred) {
+ switch (pred) {
+ default: assert(! "Unknown icmp predicate!");
+ case ICMP_EQ: case ICMP_NE:
+ case ICMP_UGT: case ICMP_ULT: case ICMP_UGE: case ICMP_ULE:
+ return pred;
+ case ICMP_SGT: return ICMP_UGT;
+ case ICMP_SLT: return ICMP_ULT;
+ case ICMP_SGE: return ICMP_UGE;
+ case ICMP_SLE: return ICMP_ULE;
+ }
+}
+
bool ICmpInst::isSignedPredicate(Predicate pred) {
switch (pred) {
default: assert(! "Unknown icmp predicate!");
diff --git a/test/Transforms/InstCombine/2008-01-21-MismatchedCastAndCompare.ll b/test/Transforms/InstCombine/2008-01-21-MismatchedCastAndCompare.ll
new file mode 100644
index 0000000..12bfb80
--- /dev/null
+++ b/test/Transforms/InstCombine/2008-01-21-MismatchedCastAndCompare.ll
@@ -0,0 +1,17 @@
+; RUN: llvm-as < %s | opt -instcombine | notcast
+; RUN: llvm-as < %s | opt -instcombine | not grep {icmp s}
+; PR1940
+
+define i1 @test1(i8 %A, i8 %B) {
+ %a = zext i8 %A to i32
+ %b = zext i8 %B to i32
+ %c = icmp sgt i32 %a, %b
+ ret i1 %c
+}
+
+define i1 @test2(i8 %A, i8 %B) {
+ %a = sext i8 %A to i32
+ %b = sext i8 %B to i32
+ %c = icmp ugt i32 %a, %b
+ ret i1 %c
+}