[llvm] r252236 - Re-apply r251050 with a for PR25421
Sanjoy Das via llvm-commits
llvm-commits at lists.llvm.org
Thu Nov 5 15:45:38 PST 2015
Author: sanjoy
Date: Thu Nov 5 17:45:38 2015
New Revision: 252236
URL: http://llvm.org/viewvc/llvm-project?rev=252236&view=rev
Log:
Re-apply r251050 with a for PR25421
The bug: I missed adding break statements in the switch / case.
Original commit message:
[SCEV] Teach SCEV some axioms about non-wrapping arithmetic
Summary:
- A s< (A + C)<nsw> if C > 0
- A s<= (A + C)<nsw> if C >= 0
- (A + C)<nsw> s< A if C < 0
- (A + C)<nsw> s<= A if C <= 0
Right now `C` needs to be a constant, but we can later generalize it to
be a non-constant if needed.
Reviewers: atrick, hfinkel, reames, nlewycky
Subscribers: sanjoy, llvm-commits
Differential Revision: http://reviews.llvm.org/D13686
Added:
llvm/trunk/test/Transforms/IndVarSimplify/pr25421.ll
Modified:
llvm/trunk/include/llvm/Analysis/ScalarEvolution.h
llvm/trunk/lib/Analysis/ScalarEvolution.cpp
llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll
Modified: llvm/trunk/include/llvm/Analysis/ScalarEvolution.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/ScalarEvolution.h?rev=252236&r1=252235&r2=252236&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Analysis/ScalarEvolution.h (original)
+++ llvm/trunk/include/llvm/Analysis/ScalarEvolution.h Thu Nov 5 17:45:38 2015
@@ -732,6 +732,14 @@ namespace llvm {
bool isKnownPredicateWithRanges(ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS);
+ /// Try to prove the condition described by "LHS Pred RHS" by ruling out
+ /// integer overflow.
+ ///
+ /// For instance, this will return true for "A s< (A + C)<nsw>" if C is
+ /// positive.
+ bool isKnownPredicateViaNoOverflow(ICmpInst::Predicate Pred,
+ const SCEV *LHS, const SCEV *RHS);
+
/// Try to split Pred LHS RHS into logical conjunctions (and's) and try to
/// prove them individually.
bool isKnownPredicateViaSplitting(ICmpInst::Predicate Pred, const SCEV *LHS,
Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=252236&r1=252235&r2=252236&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Thu Nov 5 17:45:38 2015
@@ -7348,6 +7348,62 @@ ScalarEvolution::isKnownPredicateWithRan
return false;
}
+bool ScalarEvolution::isKnownPredicateViaNoOverflow(ICmpInst::Predicate Pred,
+ const SCEV *LHS,
+ const SCEV *RHS) {
+
+ // Match Result to (X + Y)<ExpectedFlags> where Y is a constant integer.
+ // Return Y via OutY.
+ auto MatchBinaryAddToConst =
+ [this](const SCEV *Result, const SCEV *X, APInt &OutY,
+ SCEV::NoWrapFlags ExpectedFlags) {
+ const SCEV *NonConstOp, *ConstOp;
+ SCEV::NoWrapFlags FlagsPresent;
+
+ if (!splitBinaryAdd(Result, ConstOp, NonConstOp, FlagsPresent) ||
+ !isa<SCEVConstant>(ConstOp) || NonConstOp != X)
+ return false;
+
+ OutY = cast<SCEVConstant>(ConstOp)->getValue()->getValue();
+ return (FlagsPresent & ExpectedFlags) == ExpectedFlags;
+ };
+
+ APInt C;
+
+ switch (Pred) {
+ default:
+ break;
+
+ case ICmpInst::ICMP_SGE:
+ std::swap(LHS, RHS);
+ case ICmpInst::ICMP_SLE:
+ // X s<= (X + C)<nsw> if C >= 0
+ if (MatchBinaryAddToConst(RHS, LHS, C, SCEV::FlagNSW) && C.isNonNegative())
+ return true;
+
+ // (X + C)<nsw> s<= X if C <= 0
+ if (MatchBinaryAddToConst(LHS, RHS, C, SCEV::FlagNSW) &&
+ !C.isStrictlyPositive())
+ return true;
+ break;
+
+ case ICmpInst::ICMP_SGT:
+ std::swap(LHS, RHS);
+ case ICmpInst::ICMP_SLT:
+ // X s< (X + C)<nsw> if C > 0
+ if (MatchBinaryAddToConst(RHS, LHS, C, SCEV::FlagNSW) &&
+ C.isStrictlyPositive())
+ return true;
+
+ // (X + C)<nsw> s< X if C < 0
+ if (MatchBinaryAddToConst(LHS, RHS, C, SCEV::FlagNSW) && C.isNegative())
+ return true;
+ break;
+ }
+
+ return false;
+}
+
bool ScalarEvolution::isKnownPredicateViaSplitting(ICmpInst::Predicate Pred,
const SCEV *LHS,
const SCEV *RHS) {
@@ -8004,7 +8060,8 @@ ScalarEvolution::isImpliedCondOperandsHe
[this](ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS) {
return isKnownPredicateWithRanges(Pred, LHS, RHS) ||
IsKnownPredicateViaMinOrMax(*this, Pred, LHS, RHS) ||
- IsKnownPredicateViaAddRecStart(*this, Pred, LHS, RHS);
+ IsKnownPredicateViaAddRecStart(*this, Pred, LHS, RHS) ||
+ isKnownPredicateViaNoOverflow(Pred, LHS, RHS);
};
switch (Pred) {
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=252236&r1=252235&r2=252236&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll (original)
+++ llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll Thu Nov 5 17:45:38 2015
@@ -447,6 +447,64 @@ define void @func_20(i32* %length.ptr) {
ret void
}
+define void @func_21(i32* %length.ptr) {
+; CHECK-LABEL: @func_21(
+
+; This checks that the backedge condition, (I + 1) < Length - 1 implies
+; (I + 1) < Length
+ entry:
+ %length = load i32, i32* %length.ptr, !range !0
+ %lim = sub i32 %length, 1
+ %entry.cond = icmp sgt i32 %length, 1
+ br i1 %entry.cond, label %loop, label %leave
+
+ loop:
+; CHECK: loop:
+ %iv = phi i32 [ 0, %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, %lim
+ br i1 %be.cond, label %loop, label %leave
+
+ leave:
+ ret void
+}
+
+define void @func_22(i32* %length.ptr) {
+; CHECK-LABEL: @func_22(
+
+; This checks that the backedge condition, (I + 1) < Length - 1 implies
+; (I + 1) < Length
+ entry:
+ %length = load i32, i32* %length.ptr, !range !0
+ %lim = sub i32 %length, 1
+ %entry.cond = icmp sgt i32 %length, 1
+ br i1 %entry.cond, label %loop, label %leave
+
+ loop:
+; CHECK: loop:
+ %iv = phi i32 [ 0, %entry ], [ %iv.inc, %be ]
+ %iv.inc = add i32 %iv, 1
+ %range.check = icmp sle 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 sle i32 %iv.inc, %lim
+ br i1 %be.cond, label %loop, label %leave
+
+ leave:
+ ret void
+}
+
define void @func_23(i32* %length.ptr) {
; CHECK-LABEL: @func_23(
entry:
Added: llvm/trunk/test/Transforms/IndVarSimplify/pr25421.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/pr25421.ll?rev=252236&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/pr25421.ll (added)
+++ llvm/trunk/test/Transforms/IndVarSimplify/pr25421.ll Thu Nov 5 17:45:38 2015
@@ -0,0 +1,30 @@
+; RUN: opt -S -indvars < %s | FileCheck %s
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.11.0"
+
+declare void @use(i1)
+
+define void @f(i32 %x) {
+; CHECK-LABEL: @f(
+ entry:
+ %conv = sext i32 %x to i64
+ %sub = add i64 %conv, -1
+ %ec = icmp sgt i32 %x, 0
+ br i1 %ec, label %loop, label %leave
+
+ loop:
+; CHECK: loop:
+ %iv = phi i64 [ 0, %entry ], [ %iv.inc, %loop ]
+ %iv.inc = add i64 %iv, 1
+ %cmp = icmp slt i64 %iv, %sub
+ call void @use(i1 %cmp)
+; CHECK: call void @use(i1 %cmp)
+; CHECK-NOT: call void @use(i1 true)
+
+ %be.cond = icmp slt i64 %iv.inc, %conv
+ br i1 %be.cond, label %loop, label %leave
+
+ leave:
+ ret void
+}
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