[WebAssembly] Fix dominance check for PHIs in the StoreResult pass

When a block has no terminator instructions, getFirstTerminator() returns
end(), which can't be used in dominance checks. Check dominance for phi
operands separately.

Also, remove some bits from WebAssemblyRegStackify.cpp that were causing
trouble on the same testcase; they were left behind from an earlier
experiment.

Differential Revision: http://reviews.llvm.org/D15210

llvm-svn: 254662

1 files changed, 4 insertions, 5 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
index bdccc85..ecbbc5c 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
@@ -81,6 +81,7 @@ static void ImposeStackOrdering(MachineInstr *MI) {
 // more precise.
 static bool IsSafeToMove(const MachineInstr *Def, const MachineInstr *Insert,
                          AliasAnalysis &AA) {
+  assert(Def->getParent() == Insert->getParent());
   bool SawStore = false, SawSideEffects = false;
   MachineBasicBlock::const_iterator D(Def), I(Insert);
   for (--I; I != D; --I)
@@ -155,17 +156,15 @@ bool WebAssemblyRegStackify::runOnMachineFunction(MachineFunction &MF) {
             Def->getOpcode() == WebAssembly::ARGUMENT_F64)
           continue;
 
-        // Single-use expression trees require defs that have one use, or that
-        // they be trivially clonable.
+        // Single-use expression trees require defs that have one use.
         // TODO: Eventually we'll relax this, to take advantage of set_local
         // returning its result.
         if (!MRI.hasOneUse(Reg))
           continue;
 
-        // For now, be conservative and don't look across block boundaries,
-        // unless we have something trivially clonable.
+        // For now, be conservative and don't look across block boundaries.
         // TODO: Be more aggressive.
-        if (Def->getParent() != &MBB && !Def->isMoveImmediate())
+        if (Def->getParent() != &MBB)
           continue;
 
         // Don't move instructions that have side effects or memory dependencies