[PATCH] D52709: Add -instcombine-code-sinking option

[Gabor Buella via Phabricator via llvm-commits]

GBuella created this revision.
GBuella added reviewers: craig.topper, andrew.w.kaylor.
Herald added a subscriber: llvm-commits.

Repository:
  rL LLVM

https://reviews.llvm.org/D52709

Files:
  lib/Transforms/InstCombine/InstructionCombining.cpp
  test/Transforms/InstCombine/no_sink_instruction.ll


Index: test/Transforms/InstCombine/no_sink_instruction.ll
===================================================================
--- /dev/null
+++ test/Transforms/InstCombine/no_sink_instruction.ll
@@ -0,0 +1,19 @@
+; RUN: opt -instcombine -instcombine-code-sinking=0 -S < %s | FileCheck %s
+
+define i32 @test(i1 %C, i32 %A, i32 %B) {
+; CHECK-LABEL: @test(
+; CHECK: sdiv i32
+; CHECK-NEXT: add i32
+entry:
+        %tmp.2 = sdiv i32 %A, %B                ; <i32> [#uses=1]
+        %tmp.9 = add i32 %B, %A         ; <i32> [#uses=1]
+        br i1 %C, label %then, label %endif
+
+then:           ; preds = %entry
+; CHECK: ret i32
+        ret i32 %tmp.9
+
+endif:          ; preds = %entry
+; CHECK: ret i32
+        ret i32 %tmp.2
+}
Index: lib/Transforms/InstCombine/InstructionCombining.cpp
===================================================================
--- lib/Transforms/InstCombine/InstructionCombining.cpp
+++ lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -119,6 +119,10 @@
 DEBUG_COUNTER(VisitCounter, "instcombine-visit",
               "Controls which instructions are visited");
 
+static cl::opt<bool>
+CodeSinking("instcombine-code-sinking", cl::desc("Enable code sinking"),
+                                        cl::Hidden, cl::init(true));
+
 static cl::opt<bool>
 EnableExpensiveCombines("expensive-combines",
                         cl::desc("Enable expensive instruction combines"));
@@ -3088,7 +3092,7 @@
     }
 
     // See if we can trivially sink this instruction to a successor basic block.
-    if (I->hasOneUse()) {
+    if (CodeSinking && I->hasOneUse()) {
       BasicBlock *BB = I->getParent();
       Instruction *UserInst = cast<Instruction>(*I->user_begin());
       BasicBlock *UserParent;


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