[PATCH] D27722: [GVNHoist] Move GVNHoist to function simplification part of pipeline.

[Geoff Berry via Phabricator via llvm-commits]

gberry created this revision.
gberry added reviewers: sebpop, dberlin, hiraditya.
gberry added a subscriber: llvm-commits.
Herald added subscribers: mcrosier, mehdi_amini, aemerson.

Move GVNHoist to later in the optimization pipeline, specifically, to
the function simplification part of the pipeline.  The new pipeline
location allows GVNHoist to run on a function after its callees have
been inlined but before the function has been considered for inlining
into its callers, exposing more opportunities for hoisting.

Performance results on AArch64 kryo:
Improvements:

  Benchmarks/CoyoteBench/fftbench  -24.952%
  spec2006/bzip2                    -4.071%
  internal bmark                    -3.177%
  Benchmarks/PAQ8p/paq8p            -1.754%
  spec2000/perlbmk                  -1.328%
  spec2006/h264ref                  -1.140%

Regressions:

  internal bmark                    +1.818%
  Benchmarks/mafft/pairlocalalign   +1.084%


https://reviews.llvm.org/D27722

Files:
  lib/Transforms/IPO/PassManagerBuilder.cpp
  test/Transforms/GVNHoist/hoist-inline.ll


Index: test/Transforms/GVNHoist/hoist-inline.ll
===================================================================
--- /dev/null
+++ test/Transforms/GVNHoist/hoist-inline.ll
@@ -0,0 +1,38 @@
+; RUN: opt -S -O2 < %s | FileCheck %s
+
+; Check that the inlined loads are hoisted.
+; CHECK-LABEL: define i32 @fun(
+; CHECK-LABEL: entry:
+; CHECK: load i32, i32* @A
+; CHECK: if.then:
+
+ at A = external global i32
+ at B = external global i32
+ at C = external global i32
+
+define i32 @loadA() {
+   %a = load i32, i32* @A
+   ret i32 %a
+}
+
+define i32 @fun(i1 %c) {
+entry:
+  br i1 %c, label %if.then, label %if.else
+
+if.then:
+  store i32 1, i32* @B
+  %call1 = call i32 @loadA()
+  store i32 2, i32* @C
+  br label %if.endif
+
+if.else:
+  store i32 2, i32* @C
+  %call2 = call i32 @loadA()
+  store i32 1, i32* @B
+  br label %if.endif
+
+if.endif:
+  %ret = phi i32 [ %call1, %if.then ], [ %call2, %if.else ]
+  ret i32 %ret
+}
+
Index: lib/Transforms/IPO/PassManagerBuilder.cpp
===================================================================
--- lib/Transforms/IPO/PassManagerBuilder.cpp
+++ lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -249,8 +249,6 @@
   FPM.add(createCFGSimplificationPass());
   FPM.add(createSROAPass());
   FPM.add(createEarlyCSEPass());
-  if(EnableGVNHoist)
-    FPM.add(createGVNHoistPass());
   FPM.add(createLowerExpectIntrinsicPass());
 }
 
@@ -295,6 +293,8 @@
   // Break up aggregate allocas, using SSAUpdater.
   MPM.add(createSROAPass());
   MPM.add(createEarlyCSEPass());              // Catch trivial redundancies
+  if(EnableGVNHoist)
+    MPM.add(createGVNHoistPass());
   // Speculative execution if the target has divergent branches; otherwise nop.
   MPM.add(createSpeculativeExecutionIfHasBranchDivergencePass());
   MPM.add(createJumpThreadingPass());         // Thread jumps.


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