[llvm] [FuncSpec] Handle ssa_copy intrinsic calls in InstCostVisitor (PR #114247)

[Hari Limaye via llvm-commits]

https://github.com/hazzlim created https://github.com/llvm/llvm-project/pull/114247

Look through ssa_copy intrinsic calls when computing codesize bonus for a specialization.

Also remove redundant logic to skip computing codesize bonus for ssa_copy intrinsics, now these are considered zero-cost by TTI (in PR#75294).

>From 64b91defdd5a7a67b235658b26be44edfdabb413 Mon Sep 17 00:00:00 2001
From: Hari Limaye <hari.limaye at arm.com>
Date: Tue, 29 Oct 2024 12:39:05 +0000
Subject: [PATCH] [FuncSpec] Handle ssa_copy intrinsic calls in InstCostVisitor

Look through ssa_copy intrinsic calls when computing codesize bonus for
a specialization.

Also remove redundant logic to skip computing codesize bonus for
ssa_copy intrinsics, now these are considered zero-cost by TTI
(in PR#75294).
---
 llvm/lib/Transforms/IPO/FunctionSpecialization.cpp | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp b/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
index 919d3143a13f7e..1efec22624dd4f 100644
--- a/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
@@ -120,10 +120,6 @@ Cost InstCostVisitor::estimateBasicBlocks(
       continue;
 
     for (Instruction &I : *BB) {
-      // Disregard SSA copies.
-      if (auto *II = dyn_cast<IntrinsicInst>(&I))
-        if (II->getIntrinsicID() == Intrinsic::ssa_copy)
-          continue;
       // If it's a known constant we have already accounted for it.
       if (KnownConstants.contains(&I))
         continue;
@@ -402,6 +398,14 @@ Constant *InstCostVisitor::visitFreezeInst(FreezeInst &I) {
 }
 
 Constant *InstCostVisitor::visitCallBase(CallBase &I) {
+  assert(LastVisited != KnownConstants.end() && "Invalid iterator!");
+
+  // Look through calls to ssa_copy intrinsics.
+  if (auto *II = dyn_cast<IntrinsicInst>(&I);
+      II && II->getIntrinsicID() == Intrinsic::ssa_copy) {
+    return LastVisited->second;
+  }
+
   Function *F = I.getCalledFunction();
   if (!F || !canConstantFoldCallTo(&I, F))
     return nullptr;