[PowerPC] Add a late MI-level pass for QPX load/splat simplification

Chapter 3 of the QPX manual states that, "Scalar floating-point load
instructions, defined in the Power ISA, cause a replication of the source data
across all elements of the target register." Thus, if we have a load followed
by a QPX splat (from the first lane), the splat is redundant. This adds a late
MI-level pass to remove the redundant splats in some of these cases
(specifically when both occur in the same basic block).

This optimization is scheduled just prior to post-RA scheduling. It can't happen
before anything that might replace the load with some already-computed quantity
(i.e. store-to-load forwarding).

llvm-svn: 265047

1 files changed, 83 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/PowerPC/qpx-load-splat.ll b/llvm/test/CodeGen/PowerPC/qpx-load-splat.ll
new file mode 100644
index 00000000000..9feceb996a6
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/qpx-load-splat.ll
@@ -0,0 +1,83 @@
+; RUN: llc < %s | FileCheck %s
+target datalayout = "E-m:e-i64:64-n32:64"
+target triple = "powerpc64-bgq-linux"
+
+; Function Attrs: norecurse nounwind readonly
+define <4 x double> @foo(double* nocapture readonly %a) #0 {
+entry:
+  %0 = load double, double* %a, align 8, !tbaa !1
+  %vecinit.i = insertelement <4 x double> undef, double %0, i32 0
+  %shuffle.i = shufflevector <4 x double> %vecinit.i, <4 x double> undef, <4 x i32> zeroinitializer
+  ret <4 x double> %shuffle.i
+
+; CHECK-LABEL: @foo
+; CHECK: lfd 1, 0(3)
+; CHECK: blr
+}
+
+define <4 x double> @foox(double* nocapture readonly %a, i64 %idx) #0 {
+entry:
+  %p = getelementptr double, double* %a, i64 %idx
+  %0 = load double, double* %p, align 8, !tbaa !1
+  %vecinit.i = insertelement <4 x double> undef, double %0, i32 0
+  %shuffle.i = shufflevector <4 x double> %vecinit.i, <4 x double> undef, <4 x i32> zeroinitializer
+  ret <4 x double> %shuffle.i
+
+; CHECK-LABEL: @foox
+; CHECK: sldi [[REG1:[0-9]+]], 4, 3
+; CHECK: lfdx 1, 3, [[REG1]]
+; CHECK: blr
+}
+
+define <4 x double> @fooxu(double* nocapture readonly %a, i64 %idx, double** %pptr) #0 {
+entry:
+  %p = getelementptr double, double* %a, i64 %idx
+  %0 = load double, double* %p, align 8, !tbaa !1
+  %vecinit.i = insertelement <4 x double> undef, double %0, i32 0
+  %shuffle.i = shufflevector <4 x double> %vecinit.i, <4 x double> undef, <4 x i32> zeroinitializer
+  store double* %p, double** %pptr, align 8
+  ret <4 x double> %shuffle.i
+
+; CHECK-LABEL: @foox
+; CHECK: sldi [[REG1:[0-9]+]], 4, 3
+; CHECK: lfdux 1, 3, [[REG1]]
+; CHECK: std 3, 0(5)
+; CHECK: blr
+}
+
+define <4 x float> @foof(float* nocapture readonly %a) #0 {
+entry:
+  %0 = load float, float* %a, align 4, !tbaa !1
+  %vecinit.i = insertelement <4 x float> undef, float %0, i32 0
+  %shuffle.i = shufflevector <4 x float> %vecinit.i, <4 x float> undef, <4 x i32> zeroinitializer
+  ret <4 x float> %shuffle.i
+
+; CHECK-LABEL: @foof
+; CHECK: lfs 1, 0(3)
+; CHECK: blr
+}
+
+define <4 x float> @foofx(float* nocapture readonly %a, i64 %idx) #0 {
+entry:
+  %p = getelementptr float, float* %a, i64 %idx
+  %0 = load float, float* %p, align 4, !tbaa !1
+  %vecinit.i = insertelement <4 x float> undef, float %0, i32 0
+  %shuffle.i = shufflevector <4 x float> %vecinit.i, <4 x float> undef, <4 x i32> zeroinitializer
+  ret <4 x float> %shuffle.i
+
+; CHECK-LABEL: @foofx
+; CHECK: sldi [[REG1:[0-9]+]], 4, 2
+; CHECK: lfsx 1, 3, [[REG1]]
+; CHECK: blr
+}
+
+attributes #0 = { norecurse nounwind readonly "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="a2q" "target-features"="+qpx,-altivec,-bpermd,-crypto,-direct-move,-extdiv,-power8-vector,-vsx" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.ident = !{!0}
+
+!0 = !{!"bgclang r264510-20160326 clang version 3.9.0  (based on LLVM 3.9.0svn)"}
+!1 = !{!2, !2, i64 0}
+!2 = !{!"double", !3, i64 0}
+!3 = !{!"omnipotent char", !4, i64 0}
+!4 = !{!"Simple C/C++ TBAA"}
+