[llvm] r314881 - [IRCE] Temporarily disable unsigned latch conditions by default
Max Kazantsev via llvm-commits
llvm-commits at lists.llvm.org
Tue Oct 3 23:53:23 PDT 2017
Author: mkazantsev
Date: Tue Oct 3 23:53:22 2017
New Revision: 314881
URL: http://llvm.org/viewvc/llvm-project?rev=314881&view=rev
Log:
[IRCE] Temporarily disable unsigned latch conditions by default
We have found some corner cases connected to range intersection where IRCE makes
a bad thing when the latch condition is unsigned. The fix for that will go as a follow up.
This patch temporarily disables IRCE for unsigned latch conditions until the issue is fixed.
The unsigned latch conditions were introduced to IRCE by rL310027.
Differential Revision: https://reviews.llvm.org/D38529
Added:
llvm/trunk/test/Transforms/IRCE/range_intersect_miscompile.ll
Modified:
llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
llvm/trunk/test/Transforms/IRCE/clamp.ll
llvm/trunk/test/Transforms/IRCE/eq_ne.ll
llvm/trunk/test/Transforms/IRCE/stride_more_than_1.ll
llvm/trunk/test/Transforms/IRCE/unsigned_comparisons_ugt.ll
llvm/trunk/test/Transforms/IRCE/unsigned_comparisons_ult.ll
Modified: llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp?rev=314881&r1=314880&r2=314881&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp Tue Oct 3 23:53:22 2017
@@ -79,6 +79,9 @@ static cl::opt<int> MaxExitProbReciproca
static cl::opt<bool> SkipProfitabilityChecks("irce-skip-profitability-checks",
cl::Hidden, cl::init(false));
+static cl::opt<bool> AllowUnsignedLatchCondition("irce-allow-unsigned-latch",
+ cl::Hidden, cl::init(false));
+
static const char *ClonedLoopTag = "irce.loop.clone";
#define DEBUG_TYPE "irce"
@@ -889,6 +892,15 @@ LoopStructure::parseLoopStructure(Scalar
IsSignedPredicate =
Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SGT;
+
+ // FIXME: We temporarily disable unsigned latch conditions by default
+ // because of found problems with intersecting signed and unsigned ranges.
+ // We are going to turn it on once the problems are fixed.
+ if (!IsSignedPredicate && !AllowUnsignedLatchCondition) {
+ FailureReason = "unsigned latch conditions are explicitly prohibited";
+ return None;
+ }
+
// The predicate that we need to check that the induction variable lies
// within bounds.
ICmpInst::Predicate BoundPred =
@@ -964,6 +976,15 @@ LoopStructure::parseLoopStructure(Scalar
IsSignedPredicate =
Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SGT;
+
+ // FIXME: We temporarily disable unsigned latch conditions by default
+ // because of found problems with intersecting signed and unsigned ranges.
+ // We are going to turn it on once the problems are fixed.
+ if (!IsSignedPredicate && !AllowUnsignedLatchCondition) {
+ FailureReason = "unsigned latch conditions are explicitly prohibited";
+ return None;
+ }
+
// The predicate that we need to check that the induction variable lies
// within bounds.
ICmpInst::Predicate BoundPred =
Modified: llvm/trunk/test/Transforms/IRCE/clamp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IRCE/clamp.ll?rev=314881&r1=314880&r2=314881&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IRCE/clamp.ll (original)
+++ llvm/trunk/test/Transforms/IRCE/clamp.ll Tue Oct 3 23:53:22 2017
@@ -1,4 +1,4 @@
-; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -S < %s 2>&1 | FileCheck %s
+; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -irce-allow-unsigned-latch=true -S < %s 2>&1 | FileCheck %s
; The test demonstrates that incorrect behavior of Clamp may lead to incorrect
; calculation of post-loop exit condition.
Modified: llvm/trunk/test/Transforms/IRCE/eq_ne.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IRCE/eq_ne.ll?rev=314881&r1=314880&r2=314881&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IRCE/eq_ne.ll (original)
+++ llvm/trunk/test/Transforms/IRCE/eq_ne.ll Tue Oct 3 23:53:22 2017
@@ -1,4 +1,4 @@
-; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -S < %s 2>&1 | FileCheck %s
+; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -irce-allow-unsigned-latch=true -S < %s 2>&1 | FileCheck %s
; CHECK: irce: in function test_01: constrained Loop at depth 1 containing: %loop<header><exiting>,%in.bounds<latch><exiting>
; CHECK: irce: in function test_01u: constrained Loop at depth 1 containing: %loop<header><exiting>,%in.bounds<latch><exiting>
Added: llvm/trunk/test/Transforms/IRCE/range_intersect_miscompile.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IRCE/range_intersect_miscompile.ll?rev=314881&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/IRCE/range_intersect_miscompile.ll (added)
+++ llvm/trunk/test/Transforms/IRCE/range_intersect_miscompile.ll Tue Oct 3 23:53:22 2017
@@ -0,0 +1,45 @@
+; RUN: opt -irce -S < %s 2>&1 | FileCheck %s
+
+; This test demonstrates a miscompile: the outer loop's IV iterates in range of
+; [2, 400) and the range check is done against value 331. Due to a bug in range
+; intersection IRCE manages to eliminate the range check without inserting a
+; postloop, which is incorrect. So far IRCE is prohibited for this case.
+
+define void @test_01() {
+
+; CHECK-LABEL: test_01
+; CHECK-NOT: br i1 true
+
+entry:
+ br label %loop_header
+
+loop_header: ; preds = %loop_latch, %entry
+ %iv = phi i32 [ 2, %entry ], [ %iv_next, %loop_latch ]
+ %iv.prev = phi i32 [ 1, %entry ], [ %iv, %loop_latch ]
+ %tmp2 = icmp sgt i32 %iv.prev, -1
+ br i1 %tmp2, label %loop_header.split.us, label %exit
+
+loop_header.split.us: ; preds = %loop_header
+ br label %inner_loop
+
+inner_loop: ; preds = %inner_loop, %loop_header.split.us
+ %inner_iv = phi i32 [ 1, %loop_header.split.us ], [ %inner_iv_next, %inner_loop ]
+ %inner_iv_next = add nuw nsw i32 %inner_iv, 1
+ %inner_cond = icmp ult i32 %inner_iv_next, 31
+ br i1 %inner_cond, label %inner_loop, label %range_check_block
+
+exit: ; preds = %loop_latch, %loop_header
+ ret void
+
+range_check_block: ; preds = %inner_loop
+ %range_check = icmp slt i32 %iv, 331
+ br i1 %range_check, label %loop_latch, label %deopt
+
+loop_latch: ; preds = %range_check_block
+ %iv_next = add i32 %iv, 1
+ %loop_cond = icmp ult i32 %iv_next, 400
+ br i1 %loop_cond, label %loop_header, label %exit
+
+deopt: ; preds = %range_check_block
+ ret void
+}
Modified: llvm/trunk/test/Transforms/IRCE/stride_more_than_1.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IRCE/stride_more_than_1.ll?rev=314881&r1=314880&r2=314881&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IRCE/stride_more_than_1.ll (original)
+++ llvm/trunk/test/Transforms/IRCE/stride_more_than_1.ll Tue Oct 3 23:53:22 2017
@@ -1,4 +1,4 @@
-; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -S < %s 2>&1 | FileCheck %s
+; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -irce-allow-unsigned-latch=true -S < %s 2>&1 | FileCheck %s
; CHECK: irce: in function test_01: constrained Loop at depth 1 containing: %loop<header><exiting>,%in.bounds<latch><exiting>
; CHECK: irce: in function test_02: constrained Loop at depth 1 containing: %loop<header><exiting>,%in.bounds<latch><exiting>
Modified: llvm/trunk/test/Transforms/IRCE/unsigned_comparisons_ugt.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IRCE/unsigned_comparisons_ugt.ll?rev=314881&r1=314880&r2=314881&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IRCE/unsigned_comparisons_ugt.ll (original)
+++ llvm/trunk/test/Transforms/IRCE/unsigned_comparisons_ugt.ll Tue Oct 3 23:53:22 2017
@@ -1,4 +1,4 @@
-; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -S < %s 2>&1 | FileCheck %s
+; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -irce-allow-unsigned-latch=true -S < %s 2>&1 | FileCheck %s
; CHECK: irce: in function test_01: constrained Loop at depth 1 containing: %loop<header><exiting>,%in.bounds<latch><exiting>
; CHECK: irce: in function test_02: constrained Loop at depth 1 containing: %loop<header><exiting>,%in.bounds<latch><exiting>
Modified: llvm/trunk/test/Transforms/IRCE/unsigned_comparisons_ult.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IRCE/unsigned_comparisons_ult.ll?rev=314881&r1=314880&r2=314881&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IRCE/unsigned_comparisons_ult.ll (original)
+++ llvm/trunk/test/Transforms/IRCE/unsigned_comparisons_ult.ll Tue Oct 3 23:53:22 2017
@@ -1,4 +1,4 @@
-; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -S < %s 2>&1 | FileCheck %s
+; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -irce-allow-unsigned-latch=true -S < %s 2>&1 | FileCheck %s
; CHECK: irce: in function test_01: constrained Loop at depth 1 containing: %loop<header><exiting>,%in.bounds<latch><exiting>
; CHECK: irce: in function test_02: constrained Loop at depth 1 containing: %loop<header><exiting>,%in.bounds<latch><exiting>
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