[Hexagon] Remove unsafe load instructions that affect Stack Slot Coloring

The Stack slot coloring pass removes a store that is followed by a load
that deal with the same stack slot. The function isLoadFromStackSlot
is supposed to consider the loads that have no side-effects. This
patch fixed the issue by removing the unsafe loads from this function
Eg:
%vreg0<def> = L2_loadruh_io <fi#15>, 0
S2_storeri_io <fi#15>, 0, %vreg0

In this case, we load an unsigned extended half word and store this in to
the same stack slot. The Stack slot coloring pass considers safe to remove
the store. This patch marked all the non-vector byte and half word loads as
unsafe.

llvm-svn: 286843

2 files changed, 131 insertions, 12 deletions

diff --git a/llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp b/llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp
index 5c1c22f52f0..65ac1f06916 100644
--- a/llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp
@@ -240,10 +240,6 @@ unsigned HexagonInstrInfo::isLoadFromStackSlot(const MachineInstr &MI,
   switch (MI.getOpcode()) {
   default:
     break;
-  case Hexagon::L2_loadrb_io:
-  case Hexagon::L2_loadrub_io:
-  case Hexagon::L2_loadrh_io:
-  case Hexagon::L2_loadruh_io:
   case Hexagon::L2_loadri_io:
   case Hexagon::L2_loadrd_io:
   case Hexagon::V6_vL32b_ai:
@@ -266,14 +262,6 @@ unsigned HexagonInstrInfo::isLoadFromStackSlot(const MachineInstr &MI,
     return MI.getOperand(0).getReg();
   }
 
-  case Hexagon::L2_ploadrbt_io:
-  case Hexagon::L2_ploadrbf_io:
-  case Hexagon::L2_ploadrubt_io:
-  case Hexagon::L2_ploadrubf_io:
-  case Hexagon::L2_ploadrht_io:
-  case Hexagon::L2_ploadrhf_io:
-  case Hexagon::L2_ploadruht_io:
-  case Hexagon::L2_ploadruhf_io:
   case Hexagon::L2_ploadrit_io:
   case Hexagon::L2_ploadrif_io:
   case Hexagon::L2_ploadrdt_io:
diff --git a/llvm/test/CodeGen/Hexagon/dead-store-stack.ll b/llvm/test/CodeGen/Hexagon/dead-store-stack.ll
new file mode 100644
index 00000000000..93d324baad9
--- /dev/null
+++ b/llvm/test/CodeGen/Hexagon/dead-store-stack.ll
@@ -0,0 +1,131 @@
+; RUN: llc -O2 -march=hexagon < %s | FileCheck %s
+; CHECK: ParseFunc:
+; CHECK: r[[ARG0:[0-9]+]] = memuh(r[[ARG1:[0-9]+]] + #[[OFFSET:[0-9]+]])
+; CHECK: memw(r[[ARG1]]+#[[OFFSET]]) = r[[ARG0]]
+
+@.str.3 = external unnamed_addr constant [8 x i8], align 1
+; Function Attrs: nounwind
+define void @ParseFunc() local_unnamed_addr #0 {
+entry:
+  %dataVar = alloca i32, align 4
+  %0 = load i32, i32* %dataVar, align 4
+  %and = and i32 %0, 65535
+  store i32 %and, i32* %dataVar, align 4
+  %.pr = load i32, i32* %dataVar, align 4
+  switch i32 %.pr, label %sw.epilog [
+    i32 4, label %sw.bb
+    i32 5, label %sw.bb
+    i32 1, label %sw.bb39
+    i32 2, label %sw.bb40
+    i32 3, label %sw.bb41
+    i32 6, label %sw.bb42
+    i32 7, label %sw.bb43
+    i32 13, label %sw.bb44
+    i32 0, label %sw.bb44
+    i32 14, label %sw.bb45
+    i32 15, label %sw.bb46
+  ]
+
+sw.bb:
+  %cmp1.i = icmp eq i32 %.pr, 4
+  br label %land.rhs.i
+
+land.rhs.i:
+  br label %ParseFuncNext.exit.i
+
+ParseFuncNext.exit.i:
+  br i1 %cmp1.i, label %if.then.i, label %if.else10.i
+
+if.then.i:
+  call void (i8*, i32, i8*, ...) @snprintf(i8* undef, i32 undef, i8* getelementptr inbounds ([8 x i8], [8 x i8]* @.str.3, i32 0, i32 0), i32 undef) #2
+  br label %if.end27.i
+
+if.else10.i:
+  unreachable
+
+if.end27.i:
+  br label %land.rhs.i
+
+sw.bb39:
+  unreachable
+
+sw.bb40:
+  unreachable
+
+sw.bb41:
+  unreachable
+
+sw.bb42:
+  %1 = load i32, i32* undef, align 4
+  %shr.i = lshr i32 %1, 16
+  br label %while.cond.i.i
+
+while.cond.i.i:
+  %2 = load i8, i8* undef, align 1
+  switch i8 %2, label %if.then4.i [
+    i8 48, label %land.end.i.i
+    i8 120, label %land.end.i.i
+    i8 37, label %do.body.i.i
+  ]
+
+land.end.i.i:
+  unreachable
+
+do.body.i.i:
+  switch i8 undef, label %if.then4.i [
+    i8 117, label %if.end40.i.i
+    i8 120, label %if.end40.i.i
+    i8 88, label %if.end40.i.i
+    i8 100, label %if.end40.i.i
+    i8 105, label %if.end40.i.i
+  ]
+
+if.end40.i.i:
+  %trunc.i = trunc i32 %shr.i to i16
+  br label %land.rhs.i126
+
+if.then4.i:
+  unreachable
+
+land.rhs.i126:
+  switch i16 %trunc.i, label %sw.epilog.i [
+    i16 1, label %sw.bb.i
+    i16 2, label %sw.bb12.i
+    i16 4, label %sw.bb16.i
+  ]
+
+sw.bb.i:
+  unreachable
+
+sw.bb12.i:
+  unreachable
+
+sw.bb16.i:
+  unreachable
+
+sw.epilog.i:
+  call void (i8*, i32, i8*, ...) @snprintf(i8* undef, i32 undef, i8* nonnull undef, i32 undef) #2
+  br label %land.rhs.i126
+
+sw.bb43:
+  unreachable
+
+sw.bb44:
+  unreachable
+
+sw.bb45:
+  unreachable
+
+sw.bb46:
+  unreachable
+
+sw.epilog:
+  ret void
+}
+
+; Function Attrs: nounwind
+declare void @snprintf(i8* nocapture, i32, i8* nocapture readonly, ...) local_unnamed_addr #1
+
+attributes #0 = { nounwind "correctly-rounded-divide-sqrt-fp-math"="false" "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-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "stack-protector-buffer-size"="8" "target-features"="+hvx" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind "correctly-rounded-divide-sqrt-fp-math"="false" "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" "no-signed-zeros-fp-math"="false" "stack-protector-buffer-size"="8" "target-features"="+hvx" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #2 = { nounwind }