[llvm] r251051 - [SCEV] Opportunistically interpret unsigned constraints as signed
Sanjoy Das via llvm-commits
llvm-commits at lists.llvm.org
Thu Oct 22 12:57:35 PDT 2015
Author: sanjoy
Date: Thu Oct 22 14:57:34 2015
New Revision: 251051
URL: http://llvm.org/viewvc/llvm-project?rev=251051&view=rev
Log:
[SCEV] Opportunistically interpret unsigned constraints as signed
Summary:
An unsigned comparision is equivalent to is corresponding signed version
if both the operands being compared are positive. Teach SCEV to use
this fact when profitable.
Reviewers: atrick, hfinkel, reames, nlewycky
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D13687
Modified:
llvm/trunk/include/llvm/IR/InstrTypes.h
llvm/trunk/lib/Analysis/ScalarEvolution.cpp
llvm/trunk/lib/IR/Instructions.cpp
llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll
Modified: llvm/trunk/include/llvm/IR/InstrTypes.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/InstrTypes.h?rev=251051&r1=251050&r2=251051&view=diff
==============================================================================
--- llvm/trunk/include/llvm/IR/InstrTypes.h (original)
+++ llvm/trunk/include/llvm/IR/InstrTypes.h Thu Oct 22 14:57:34 2015
@@ -1033,6 +1033,19 @@ public:
return isUnsigned(getPredicate());
}
+ /// For example, ULT->SLT, ULE->SLE, UGT->SGT, UGE->SGE, SLT->Failed assert
+ /// @returns the signed version of the unsigned predicate pred.
+ /// @brief return the signed version of a predicate
+ static Predicate getSignedPredicate(Predicate pred);
+
+ /// For example, ULT->SLT, ULE->SLE, UGT->SGT, UGE->SGE, SLT->Failed assert
+ /// @returns the signed version of the predicate for this instruction (which
+ /// has to be an unsigned predicate).
+ /// @brief return the signed version of a predicate
+ Predicate getSignedPredicate() {
+ return getSignedPredicate(getPredicate());
+ }
+
/// This is just a convenience.
/// @brief Determine if this is true when both operands are the same.
bool isTrueWhenEqual() const {
Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=251051&r1=251050&r2=251051&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Thu Oct 22 14:57:34 2015
@@ -7509,6 +7509,13 @@ bool ScalarEvolution::isImpliedCond(ICmp
RHS, LHS, FoundLHS, FoundRHS);
}
+ // Unsigned comparison is the same as signed comparison when both the operands
+ // are non-negative.
+ if (CmpInst::isUnsigned(FoundPred) &&
+ CmpInst::getSignedPredicate(FoundPred) == Pred &&
+ isKnownNonNegative(FoundLHS) && isKnownNonNegative(FoundRHS))
+ return isImpliedCondOperands(Pred, LHS, RHS, FoundLHS, FoundRHS);
+
// Check if we can make progress by sharpening ranges.
if (FoundPred == ICmpInst::ICMP_NE &&
(isa<SCEVConstant>(FoundLHS) || isa<SCEVConstant>(FoundRHS))) {
Modified: llvm/trunk/lib/IR/Instructions.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Instructions.cpp?rev=251051&r1=251050&r2=251051&view=diff
==============================================================================
--- llvm/trunk/lib/IR/Instructions.cpp (original)
+++ llvm/trunk/lib/IR/Instructions.cpp Thu Oct 22 14:57:34 2015
@@ -3558,6 +3558,23 @@ CmpInst::Predicate CmpInst::getSwappedPr
}
}
+CmpInst::Predicate CmpInst::getSignedPredicate(Predicate pred) {
+ assert(CmpInst::isUnsigned(pred) && "Call only with signed predicates!");
+
+ switch (pred) {
+ default:
+ llvm_unreachable("Unknown predicate!");
+ case CmpInst::ICMP_ULT:
+ return CmpInst::ICMP_SLT;
+ case CmpInst::ICMP_ULE:
+ return CmpInst::ICMP_SLE;
+ case CmpInst::ICMP_UGT:
+ return CmpInst::ICMP_SGT;
+ case CmpInst::ICMP_UGE:
+ return CmpInst::ICMP_SGE;
+ }
+}
+
bool CmpInst::isUnsigned(unsigned short predicate) {
switch (predicate) {
default: return false;
Modified: llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll?rev=251051&r1=251050&r2=251051&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll (original)
+++ llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll Thu Oct 22 14:57:34 2015
@@ -535,5 +535,55 @@ define void @func_23(i32* %length.ptr) {
ret void
}
+define void @func_24(i32* %length.ptr) {
+; CHECK-LABEL: @func_24(
+ entry:
+ %length = load i32, i32* %length.ptr, !range !0
+ %entry.cond = icmp ult i32 4, %length
+ br i1 %entry.cond, label %loop, label %leave
+
+ loop:
+; CHECK: loop:
+ %iv = phi i32 [ 4, %entry ], [ %iv.inc, %be ]
+ %iv.inc = add i32 %iv, 1
+ %range.check = icmp slt i32 %iv, %length
+ br i1 %range.check, label %be, label %leave
+; CHECK: br i1 true, label %be, label %leave.loopexit
+; CHECK: be:
+
+ be:
+ call void @side_effect()
+ %be.cond = icmp slt i32 %iv.inc, %length
+ br i1 %be.cond, label %loop, label %leave
+
+ leave:
+ ret void
+}
+
+define void @func_25(i32* %init.ptr) {
+; CHECK-LABEL: @func_25(
+ entry:
+ %init = load i32, i32* %init.ptr, !range !0
+ %entry.cond = icmp ugt i32 %init, 4
+ br i1 %entry.cond, label %loop, label %leave
+
+ loop:
+; CHECK: loop:
+ %iv = phi i32 [ %init, %entry ], [ %iv.dec, %be ]
+ %iv.dec = add i32 %iv, -1
+ %range.check = icmp sgt i32 %iv, 4
+ br i1 %range.check, label %be, label %leave
+; CHECK: br i1 true, label %be, label %leave.loopexit
+; CHECK: be:
+
+ be:
+ call void @side_effect()
+ %be.cond = icmp sgt i32 %iv.dec, 4
+ br i1 %be.cond, label %loop, label %leave
+
+ leave:
+ ret void
+}
+
!0 = !{i32 0, i32 2147483647}
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