[PATCH] D93302: Disable Jump Threading for the targets with divergent control flow

[Alexander via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG35ec3ff76dee: Disable Jump Threading for the targets with divergent control flow (authored by alex-t).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D93302/new/

https://reviews.llvm.org/D93302

Files:
  llvm/lib/Transforms/Scalar/JumpThreading.cpp
  llvm/test/Transforms/JumpThreading/divergent-target-test.ll


Index: llvm/test/Transforms/JumpThreading/divergent-target-test.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/JumpThreading/divergent-target-test.ll
@@ -0,0 +1,47 @@
+; REQUIRES: amdgpu-registered-target && x86-registered-target
+; RUN: opt < %s -mtriple=amdgcn -jump-threading -S | FileCheck %s  -check-prefixes=CHECK,DIVERGENT
+; RUN: opt < %s -mtriple=x86_64 -jump-threading -S | FileCheck %s  -check-prefixes=CHECK,UNIFORM
+
+; Here we assure that for the target with no branch divergence usual Jump Threading optimization performed
+; For target with branch divergence - no optimization, so the IR is unchanged.
+
+declare i32 @f1()
+declare i32 @f2()
+declare void @f3()
+
+define i32 @test(i1 %cond) {
+; CHECK: test
+	br i1 %cond, label %T1, label %F1
+
+; DIVERGENT:   T1
+; UNIFORM-NOT: T1
+T1:
+	%v1 = call i32 @f1()
+	br label %Merge
+; DIVERGENT:   F1
+; UNIFORM-NOT: F1
+F1:
+	%v2 = call i32 @f2()
+	br label %Merge
+; DIVERGENT:   Merge
+; UNIFORM-NOT: Merge
+Merge:
+	%A = phi i1 [true, %T1], [false, %F1]
+	%B = phi i32 [%v1, %T1], [%v2, %F1]
+	br i1 %A, label %T2, label %F2
+
+; DIVERGENT:   T2
+T2:
+; UNIFORM: T2:
+; UNIFORM: %v1 = call i32 @f1()
+; UNIFORM: call void @f3()
+; UNIFORM: ret i32 %v1
+	call void @f3()
+	ret i32 %B
+; DIVERGENT:   F2
+F2:
+; UNIFORM: F2:
+; UNIFORM: %v2 = call i32 @f2()
+; UNIFORM: ret i32 %v2
+	ret i32 %B
+}
Index: llvm/lib/Transforms/Scalar/JumpThreading.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -32,6 +32,7 @@
 #include "llvm/Analysis/Loads.h"
 #include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/CFG.h"
@@ -153,6 +154,7 @@
       AU.addPreserved<LazyValueInfoWrapperPass>();
       AU.addPreserved<GlobalsAAWrapperPass>();
       AU.addRequired<TargetLibraryInfoWrapperPass>();
+      AU.addRequired<TargetTransformInfoWrapperPass>();
     }
 
     void releaseMemory() override { Impl.releaseMemory(); }
@@ -311,6 +313,10 @@
 bool JumpThreading::runOnFunction(Function &F) {
   if (skipFunction(F))
     return false;
+  auto TTI = &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
+  // Jump Threading has no sense for the targets with divergent CF
+  if (TTI->hasBranchDivergence())
+    return false;
   auto TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
   auto DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
   auto LVI = &getAnalysis<LazyValueInfoWrapperPass>().getLVI();


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