[GVNHoist] Move GVNHoist to function simplification part of pipeline.

Summary:
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%

Reviewers: sebpop, dberlin, hiraditya

Subscribers: aemerson, mehdi_amini, mcrosier, llvm-commits

Differential Revision: https://reviews.llvm.org/D27722

llvm-svn: 289696

1 files changed, 38 insertions, 0 deletions

diff --git a/llvm/test/Transforms/GVNHoist/hoist-inline.ll b/llvm/test/Transforms/GVNHoist/hoist-inline.ll
new file mode 100644
index 00000000000..7d761486ab1
--- /dev/null
+++ b/llvm/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:
+
+@A = external global i32
+@B = external global i32
+@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
+}
+