[llvm] r307126 - [IndVars] Canonicalize comparisons between non-negative values and indvars
Max Kazantsev via llvm-commits
llvm-commits at lists.llvm.org
Tue Jul 4 23:38:49 PDT 2017
Author: mkazantsev
Date: Tue Jul 4 23:38:49 2017
New Revision: 307126
URL: http://llvm.org/viewvc/llvm-project?rev=307126&view=rev
Log:
[IndVars] Canonicalize comparisons between non-negative values and indvars
-If there is a IndVar which is known to be non-negative, and there is a value which is also non-negative,
then signed and unsigned comparisons between them produce the same result. Both of those can be
seen in the same loop. To allow other optimizations to simplify them, we turn all instructions like
%c = icmp slt i32 %iv, %b
to
%c = icmp ult i32 %iv, %b
if both %iv and %b are known to be non-negative.
Differential Revision: https://reviews.llvm.org/D34979
Added:
llvm/trunk/test/Transforms/IndVarSimplify/canonicalize-cmp.ll
Modified:
llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp
llvm/trunk/test/Analysis/ScalarEvolution/guards.ll
llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll
llvm/trunk/test/Transforms/IndVarSimplify/widen-loop-comp.ll
Modified: llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp?rev=307126&r1=307125&r2=307126&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp Tue Jul 4 23:38:49 2017
@@ -262,6 +262,10 @@ void SimplifyIndvar::eliminateIVComparis
ICmp->setPredicate(InvariantPredicate);
ICmp->setOperand(0, NewLHS);
ICmp->setOperand(1, NewRHS);
+ } else if (ICmpInst::isSigned(Pred) &&
+ SE->isKnownNonNegative(S) && SE->isKnownNonNegative(X)) {
+ DEBUG(dbgs() << "INDVARS: Turn to unsigned comparison: " << *ICmp << '\n');
+ ICmp->setPredicate(ICmpInst::getUnsignedPredicate(Pred));
} else
return;
Modified: llvm/trunk/test/Analysis/ScalarEvolution/guards.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/ScalarEvolution/guards.ll?rev=307126&r1=307125&r2=307126&view=diff
==============================================================================
--- llvm/trunk/test/Analysis/ScalarEvolution/guards.ll (original)
+++ llvm/trunk/test/Analysis/ScalarEvolution/guards.ll Tue Jul 4 23:38:49 2017
@@ -19,7 +19,7 @@ entry:
loop:
; CHECK: loop:
; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 true) [ "deopt"() ]
-; CHECK: %iv.inc.cmp = icmp slt i32 %iv.inc, %len
+; CHECK: %iv.inc.cmp = icmp ult i32 %iv.inc, %len
; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 %iv.inc.cmp) [ "deopt"() ]
; CHECK: leave:
@@ -41,7 +41,7 @@ leave:
define void @test_2(i32 %n, i32* %len_buf) {
; CHECK-LABEL: @test_2(
-; CHECK: [[LEN_SEXT:%[^ ]+]] = sext i32 %len to i64
+; CHECK: [[LEN_ZEXT:%[^ ]+]] = zext i32 %len to i64
; CHECK: br label %loop
entry:
@@ -52,7 +52,7 @@ loop:
; CHECK: loop:
; CHECK: %indvars.iv = phi i64 [ %indvars.iv.next, %loop ], [ 0, %entry ]
; CHECK: %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
-; CHECK: %iv.inc.cmp = icmp slt i64 %indvars.iv.next, [[LEN_SEXT]]
+; CHECK: %iv.inc.cmp = icmp ult i64 %indvars.iv.next, [[LEN_ZEXT]]
; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 %iv.inc.cmp) [ "deopt"() ]
; CHECK: leave:
Added: llvm/trunk/test/Transforms/IndVarSimplify/canonicalize-cmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/canonicalize-cmp.ll?rev=307126&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/canonicalize-cmp.ll (added)
+++ llvm/trunk/test/Transforms/IndVarSimplify/canonicalize-cmp.ll Tue Jul 4 23:38:49 2017
@@ -0,0 +1,52 @@
+; RUN: opt -S -indvars < %s | FileCheck %s
+
+; Check that we replace signed comparisons between non-negative values with
+; unsigned comparisons if we can.
+
+target datalayout = "n8:16:32:64"
+
+define i32 @test_01(i32 %a, i32 %b, i32* %p) {
+
+; CHECK-LABEL: @test_01(
+; CHECK-NOT: icmp slt
+; CHECK: %cmp1 = icmp ult i32 %iv, 100
+; CHECK: %cmp2 = icmp ult i32 %iv, 100
+; CHECK-NOT: %cmp3
+; CHECK: %exitcond = icmp ne i32 %iv.next, 1000
+
+entry:
+ br label %loop.entry
+
+loop.entry:
+ %iv = phi i32 [ 0, %entry ], [ %iv.next, %loop.be ]
+ %cmp1 = icmp slt i32 %iv, 100
+ br i1 %cmp1, label %b1, label %b2
+
+b1:
+ store i32 %iv, i32* %p
+ br label %merge
+
+b2:
+ store i32 %a, i32* %p
+ br label %merge
+
+merge:
+ %cmp2 = icmp ult i32 %iv, 100
+ br i1 %cmp2, label %b3, label %b4
+
+b3:
+ store i32 %iv, i32* %p
+ br label %loop.be
+
+b4:
+ store i32 %b, i32* %p
+ br label %loop.be
+
+loop.be:
+ %iv.next = add i32 %iv, 1
+ %cmp3 = icmp slt i32 %iv.next, 1000
+ br i1 %cmp3, label %loop.entry, label %exit
+
+exit:
+ ret i32 %iv
+}
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=307126&r1=307125&r2=307126&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll (original)
+++ llvm/trunk/test/Transforms/IndVarSimplify/eliminate-comparison.ll Tue Jul 4 23:38:49 2017
@@ -111,7 +111,7 @@ return:
; Indvars should not turn the second loop into an infinite one.
; CHECK-LABEL: @func_11(
-; CHECK: %tmp5 = icmp slt i32 %__key6.0, 10
+; CHECK: %tmp5 = icmp ult i32 %__key6.0, 10
; CHECK-NOT: br i1 true, label %noassert68, label %unrolledend
define i32 @func_11() nounwind uwtable {
@@ -163,7 +163,7 @@ declare void @llvm.trap() noreturn nounw
; In this case the second loop only has a single iteration, fold the header away
; CHECK-LABEL: @func_12(
-; CHECK: %tmp5 = icmp slt i32 %__key6.0, 10
+; CHECK: %tmp5 = icmp ult i32 %__key6.0, 10
; CHECK: br i1 true, label %noassert68, label %unrolledend
define i32 @func_12() nounwind uwtable {
entry:
Modified: llvm/trunk/test/Transforms/IndVarSimplify/widen-loop-comp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/widen-loop-comp.ll?rev=307126&r1=307125&r2=307126&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/widen-loop-comp.ll (original)
+++ llvm/trunk/test/Transforms/IndVarSimplify/widen-loop-comp.ll Tue Jul 4 23:38:49 2017
@@ -64,7 +64,7 @@ for.end:
; CHECK-LABEL: @test2
; CHECK: for.body4.us
; CHECK: %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
-; CHECK: %cmp2.us = icmp slt i64
+; CHECK: %cmp2.us = icmp ult i64
; CHECK-NOT: %2 = trunc i64 %indvars.iv.next to i32
; CHECK-NOT: %cmp2.us = icmp slt i32
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