Fix a stunning oversight in the inline cost analysis. It was never

propagating one of the values it simplified to a constant across
a myriad of instructions. Notably, ptrtoint instructions when we had
a constant pointer (say, 0) didn't propagate that, blocking a massive
number of down-stream optimizations.

This was uncovered when investigating why we fail to inline and delete
the boilerplate in:

  void f() {
    std::vector<int> v;
    v.push_back(1);
  }

It turns out most of the efforts I've made thus far to improve the
analysis weren't making it far purely because of this. After this is
fixed, the store-to-load forwarding patch enables LLVM to optimize the
above to an empty function. We still can't nuke a second push_back, but
for different reasons.

There is a very real chance this will cause somewhat noticable changes
in inlining behavior, so please let me know if you see regressions (or
improvements!) because of this patch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171196 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 16 insertions, 4 deletions

diff --git a/lib/Analysis/InlineCost.cpp b/lib/Analysis/InlineCost.cpp
index 685050765a..835b8343b2 100644
--- a/lib/Analysis/InlineCost.cpp
+++ b/lib/Analysis/InlineCost.cpp
@@ -358,7 +358,10 @@ bool CallAnalyzer::visitGetElementPtr(GetElementPtrInst &I) {
 
 bool CallAnalyzer::visitBitCast(BitCastInst &I) {
   // Propagate constants through bitcasts.
-  if (Constant *COp = dyn_cast<Constant>(I.getOperand(0)))
+  Constant *COp = dyn_cast<Constant>(I.getOperand(0));
+  if (!COp)
+    COp = SimplifiedValues.lookup(I.getOperand(0));
+  if (COp)
     if (Constant *C = ConstantExpr::getBitCast(COp, I.getType())) {
       SimplifiedValues[&I] = C;
       return true;
@@ -383,7 +386,10 @@ bool CallAnalyzer::visitBitCast(BitCastInst &I) {
 
 bool CallAnalyzer::visitPtrToInt(PtrToIntInst &I) {
   // Propagate constants through ptrtoint.
-  if (Constant *COp = dyn_cast<Constant>(I.getOperand(0)))
+  Constant *COp = dyn_cast<Constant>(I.getOperand(0));
+  if (!COp)
+    COp = SimplifiedValues.lookup(I.getOperand(0));
+  if (COp)
     if (Constant *C = ConstantExpr::getPtrToInt(COp, I.getType())) {
       SimplifiedValues[&I] = C;
       return true;
@@ -416,7 +422,10 @@ bool CallAnalyzer::visitPtrToInt(PtrToIntInst &I) {
 
 bool CallAnalyzer::visitIntToPtr(IntToPtrInst &I) {
   // Propagate constants through ptrtoint.
-  if (Constant *COp = dyn_cast<Constant>(I.getOperand(0)))
+  Constant *COp = dyn_cast<Constant>(I.getOperand(0));
+  if (!COp)
+    COp = SimplifiedValues.lookup(I.getOperand(0));
+  if (COp)
     if (Constant *C = ConstantExpr::getIntToPtr(COp, I.getType())) {
       SimplifiedValues[&I] = C;
       return true;
@@ -443,7 +452,10 @@ bool CallAnalyzer::visitIntToPtr(IntToPtrInst &I) {
 
 bool CallAnalyzer::visitCastInst(CastInst &I) {
   // Propagate constants through ptrtoint.
-  if (Constant *COp = dyn_cast<Constant>(I.getOperand(0)))
+  Constant *COp = dyn_cast<Constant>(I.getOperand(0));
+  if (!COp)
+    COp = SimplifiedValues.lookup(I.getOperand(0));
+  if (COp)
     if (Constant *C = ConstantExpr::getCast(I.getOpcode(), COp, I.getType())) {
       SimplifiedValues[&I] = C;
       return true;