[PATCH] D81026: Inline Cost improvement - GetElementPtr with constant operands

[Kirill Naumov via Phabricator via llvm-commits]

knaumov updated this revision to Diff 267975.
knaumov added a comment.

Answering @mtrofin 's comments:

As such cases (GEPs from a constant address with constant operands) will be simplified by the pipeline to a constant, InlineCost should be able to see this to apply the correct cost to the instruction. As eventually, the instruction will turn to a constant, the cost is 0.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D81026/new/

https://reviews.llvm.org/D81026

Files:
  llvm/lib/Analysis/InlineCost.cpp
  llvm/test/Transforms/Inline/gep_from_constant.ll


Index: llvm/test/Transforms/Inline/gep_from_constant.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/Inline/gep_from_constant.ll
@@ -0,0 +1,15 @@
+; RUN: opt < %s -passes="print<inline-cost>" 2>&1 | FileCheck %s
+
+; CHECK-LABEL: @foo
+; CHECK: cost before = {{.*}}, cost after = {{.*}}, threshold before = {{.*}}, threshold after = {{.*}}, cost delta = {{.*}}, simplified to i8 addrspace(1)** getelementptr (i8 addrspace(1)*, i8 addrspace(1)** inttoptr (i64 754974720 to i8 addrspace(1)**), i64 5)
+
+define i8 addrspace(1)** @foo(i64 %0) {
+  %2 = inttoptr i64 754974720 to i8 addrspace(1)**
+  %3 = getelementptr i8 addrspace(1)*, i8 addrspace(1)** %2, i64 %0
+  ret i8 addrspace(1)** %3
+}
+
+define i8 addrspace(1)** @main() {
+  %1 = call i8 addrspace(1)** @foo(i64 5)
+  ret i8 addrspace(1)** %1
+}
Index: llvm/lib/Analysis/InlineCost.cpp
===================================================================
--- llvm/lib/Analysis/InlineCost.cpp
+++ llvm/lib/Analysis/InlineCost.cpp
@@ -1003,6 +1003,15 @@
     return true;
   };
 
+  if (simplifyInstruction(I, [&](SmallVectorImpl<Constant *> &COps) {
+      SmallVector<Constant *, 2> Indices;
+      for (unsigned int Index = 1 ; Index < COps.size() ; ++Index)
+        Indices.push_back(COps[Index]);
+      return ConstantExpr::getGetElementPtr(I.getSourceElementType(), COps[0],
+                                            Indices, I.isInBounds());
+    }))
+    return true;
+
   if ((I.isInBounds() && canFoldInboundsGEP(I)) || IsGEPOffsetConstant(I)) {
     if (SROAArg)
       SROAArgValues[&I] = SROAArg;


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