[llvm] r352779 - Lower widenable_conditions in CGP
Philip Reames via llvm-commits
llvm-commits at lists.llvm.org
Thu Jan 31 10:45:46 PST 2019
Author: reames
Date: Thu Jan 31 10:45:46 2019
New Revision: 352779
URL: http://llvm.org/viewvc/llvm-project?rev=352779&view=rev
Log:
Lower widenable_conditions in CGP
This ensures that if we make it to the backend w/o lowering widenable_conditions first, that we generate correct code. Doing it in CGP - instead of isel - let's us fold control flow before hitting block local instruction selection.
Differential Revision: https://reviews.llvm.org/D57473
Added:
llvm/trunk/test/Transforms/CodeGenPrepare/widenable-condition.ll
Modified:
llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
Modified: llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp?rev=352779&r1=352778&r2=352779&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp (original)
+++ llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp Thu Jan 31 10:45:46 2019
@@ -1703,6 +1703,20 @@ bool CodeGenPrepare::optimizeCallInst(Ca
if (II) {
switch (II->getIntrinsicID()) {
default: break;
+ case Intrinsic::experimental_widenable_condition: {
+ // Give up on future widening oppurtunties so that we can fold away dead
+ // paths and merge blocks before going into block-local instruction
+ // selection.
+ if (II->use_empty()) {
+ II->eraseFromParent();
+ return true;
+ }
+ Constant *RetVal = ConstantInt::getTrue(II->getContext());
+ resetIteratorIfInvalidatedWhileCalling(BB, [&]() {
+ replaceAndRecursivelySimplify(CI, RetVal, TLInfo, nullptr);
+ });
+ return true;
+ }
case Intrinsic::objectsize: {
// Lower all uses of llvm.objectsize.*
Value *RetVal =
Added: llvm/trunk/test/Transforms/CodeGenPrepare/widenable-condition.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/CodeGenPrepare/widenable-condition.ll?rev=352779&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/CodeGenPrepare/widenable-condition.ll (added)
+++ llvm/trunk/test/Transforms/CodeGenPrepare/widenable-condition.ll Thu Jan 31 10:45:46 2019
@@ -0,0 +1,93 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -codegenprepare -S < %s | FileCheck %s
+
+; Check the idiomatic guard pattern to ensure it's lowered correctly.
+define void @test_guard(i1 %cond_0) {
+; CHECK-LABEL: @test_guard(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: br i1 [[COND_0:%.*]], label [[GUARDED:%.*]], label [[DEOPT:%.*]]
+; CHECK: deopt:
+; CHECK-NEXT: call void @foo()
+; CHECK-NEXT: ret void
+; CHECK: guarded:
+; CHECK-NEXT: ret void
+;
+entry:
+ %widenable_cond = call i1 @llvm.experimental.widenable.condition()
+ %exiplicit_guard_cond = and i1 %cond_0, %widenable_cond
+ br i1 %exiplicit_guard_cond, label %guarded, label %deopt
+
+deopt: ; preds = %entry
+ call void @foo()
+ ret void
+
+guarded:
+ ret void
+}
+
+;; Test a non-guard fastpath/slowpath case
+define void @test_triangle(i1 %cond_0) {
+; CHECK-LABEL: @test_triangle(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: br i1 [[COND_0:%.*]], label [[FASTPATH:%.*]], label [[SLOWPATH:%.*]]
+; CHECK: fastpath:
+; CHECK-NEXT: call void @bar()
+; CHECK-NEXT: br label [[MERGE:%.*]]
+; CHECK: slowpath:
+; CHECK-NEXT: call void @foo()
+; CHECK-NEXT: br label [[MERGE]]
+; CHECK: merge:
+; CHECK-NEXT: ret void
+;
+entry:
+ %widenable_cond = call i1 @llvm.experimental.widenable.condition()
+ %exiplicit_guard_cond = and i1 %cond_0, %widenable_cond
+ br i1 %exiplicit_guard_cond, label %fastpath, label %slowpath
+
+fastpath:
+ call void @bar()
+ br label %merge
+
+slowpath:
+ call void @foo()
+ br label %merge
+
+merge:
+ ret void
+}
+
+
+; Demonstrate that resulting CFG simplifications are made
+define void @test_cfg_simplify() {
+; CHECK-LABEL: @test_cfg_simplify(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: ret void
+;
+entry:
+ %widenable_cond3 = call i1 @llvm.experimental.widenable.condition()
+ br i1 %widenable_cond3, label %guarded2, label %deopt3
+
+deopt3:
+ call void @foo()
+ ret void
+
+guarded2:
+ %widenable_cond4 = call i1 @llvm.experimental.widenable.condition()
+ br i1 %widenable_cond4, label %merge1, label %slowpath1
+
+slowpath1:
+ call void @foo()
+ br label %merge1
+
+merge1:
+ ret void
+}
+
+
+declare void @foo()
+declare void @bar()
+
+; Function Attrs: inaccessiblememonly nounwind
+declare i1 @llvm.experimental.widenable.condition() #0
+
+attributes #0 = { inaccessiblememonly nounwind }
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