[PATCH] D44029: [MergeICmp] We can discard initial blocks that do other work
Xin Tong via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Mon Mar 5 05:57:13 PST 2018
This revision was automatically updated to reflect the committed changes.
Closed by commit rL326698: [MergeICmp] We can discard initial blocks that do other work (authored by trentxintong, committed by ).
Changed prior to commit:
https://reviews.llvm.org/D44029?vs=136788&id=136984#toc
Repository:
rL LLVM
https://reviews.llvm.org/D44029
Files:
llvm/trunk/lib/Transforms/Scalar/MergeICmps.cpp
llvm/trunk/test/Transforms/MergeICmps/X86/multiple-blocks-does-work.ll
Index: llvm/trunk/lib/Transforms/Scalar/MergeICmps.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Scalar/MergeICmps.cpp
+++ llvm/trunk/lib/Transforms/Scalar/MergeICmps.cpp
@@ -291,8 +291,8 @@
if (Comparison.doesOtherWork()) {
DEBUG(dbgs() << "block '" << Comparison.BB->getName()
<< "' does extra work besides compare\n");
- if (BlockIdx == 0) { // First block.
- // TODO(courbet): The first block can do other things, and we should
+ if (Comparisons.empty()) {
+ // TODO(courbet): The initial block can do other things, and we should
// split them apart in a separate block before the comparison chain.
// Right now we just discard it and make the chain shorter.
DEBUG(dbgs()
@@ -333,7 +333,12 @@
DEBUG(dbgs() << "\n");
Comparisons.push_back(Comparison);
}
- assert(!Comparisons.empty() && "chain with no BCE basic blocks");
+
+ // It is possible we have no suitable comparison to merge.
+ if (Comparisons.empty()) {
+ DEBUG(dbgs() << "chain with no BCE basic blocks, no merge\n");
+ return;
+ }
EntryBlock_ = Comparisons[0].BB;
Comparisons_ = std::move(Comparisons);
#ifdef MERGEICMPS_DOT_ON
Index: llvm/trunk/test/Transforms/MergeICmps/X86/multiple-blocks-does-work.ll
===================================================================
--- llvm/trunk/test/Transforms/MergeICmps/X86/multiple-blocks-does-work.ll
+++ llvm/trunk/test/Transforms/MergeICmps/X86/multiple-blocks-does-work.ll
@@ -0,0 +1,64 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -mergeicmps -mtriple=x86_64-unknown-unknown -S | FileCheck %s --check-prefix=X86
+
+%"struct.std::pair" = type { i32, i32, i32, i32 }
+
+declare void @foo(...)
+
+; We can discard %entry and %land.rhs.i, but still merge the last 2 blocks.
+define zeroext i1 @opeq1(
+; X86-LABEL: @opeq1(
+; X86: land.rhs.i.2:
+; X86-NEXT: [[THIRD_I:%.*]] = getelementptr inbounds %"struct.std::pair", %"struct.std::pair"* [[A:%.*]], i64 0, i32 2
+; X86-NEXT: [[THIRD1_I:%.*]] = getelementptr inbounds %"struct.std::pair", %"struct.std::pair"* [[B:%.*]], i64 0, i32 2
+; X86-NEXT: [[CSTR:%.*]] = bitcast i32* [[THIRD_I]] to i8*
+; X86-NEXT: [[CSTR1:%.*]] = bitcast i32* [[THIRD1_I]] to i8*
+; X86-NEXT: [[MEMCMP:%.*]] = call i32 @memcmp(i8* [[CSTR]], i8* [[CSTR1]], i64 8)
+; X86-NEXT: [[TMP0:%.*]] = icmp eq i32 [[MEMCMP]], 0
+; X86-NEXT: br label [[OPEQ1_EXIT:%.*]]
+; X86: opeq1.exit:
+; X86-NEXT: [[TMP1:%.*]] = phi i1 [ false, %entry ], [ false, %land.rhs.i ], [ [[TMP0]], %land.rhs.i.2 ]
+; X86-NEXT: ret i1 [[TMP1]]
+;
+ %"struct.std::pair"* nocapture readonly dereferenceable(16) %a,
+ %"struct.std::pair"* nocapture readonly dereferenceable(16) %b) local_unnamed_addr #0 {
+entry:
+ %first.i = getelementptr inbounds %"struct.std::pair", %"struct.std::pair"* %a, i64 0, i32 0
+ %0 = load i32, i32* %first.i, align 4
+ %first1.i = getelementptr inbounds %"struct.std::pair", %"struct.std::pair"* %b, i64 0, i32 0
+ %1 = load i32, i32* %first1.i, align 4
+ ; Does other work.
+ call void (...) @foo()
+ %cmp.i = icmp eq i32 %0, %1
+ br i1 %cmp.i, label %land.rhs.i, label %opeq1.exit
+
+land.rhs.i:
+ %second.i = getelementptr inbounds %"struct.std::pair", %"struct.std::pair"* %a, i64 0, i32 1
+ %2 = load i32, i32* %second.i, align 4
+ %second2.i = getelementptr inbounds %"struct.std::pair", %"struct.std::pair"* %b, i64 0, i32 1
+ %3 = load i32, i32* %second2.i, align 4
+ ; Does other work.
+ call void (...) @foo()
+ %cmp2.i = icmp eq i32 %2, %3
+ br i1 %cmp2.i, label %land.rhs.i.2, label %opeq1.exit
+
+land.rhs.i.2:
+ %third.i = getelementptr inbounds %"struct.std::pair", %"struct.std::pair"* %a, i64 0, i32 2
+ %4 = load i32, i32* %third.i, align 4
+ %third2.i = getelementptr inbounds %"struct.std::pair", %"struct.std::pair"* %b, i64 0, i32 2
+ %5 = load i32, i32* %third2.i, align 4
+ %cmp3.i = icmp eq i32 %4, %5
+ br i1 %cmp3.i, label %land.rhs.i.3, label %opeq1.exit
+
+land.rhs.i.3:
+ %fourth.i = getelementptr inbounds %"struct.std::pair", %"struct.std::pair"* %a, i64 0, i32 3
+ %6 = load i32, i32* %fourth.i, align 4
+ %fourth2.i = getelementptr inbounds %"struct.std::pair", %"struct.std::pair"* %b, i64 0, i32 3
+ %7 = load i32, i32* %fourth2.i, align 4
+ %cmp4.i = icmp eq i32 %6, %7
+ br label %opeq1.exit
+
+opeq1.exit:
+ %8 = phi i1 [ false, %entry ], [ false, %land.rhs.i] , [ false, %land.rhs.i.2 ], [ %cmp4.i, %land.rhs.i.3 ]
+ ret i1 %8
+}
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