[llvm-branch-commits] [llvm] release/21.x: [SystemZ] Remove incorrect areInlineCompatible hook (#152494) (PR #152660)

[Tobias Hieta via llvm-branch-commits]

https://github.com/tru updated https://github.com/llvm/llvm-project/pull/152660

>From 7be867f19d05bd93a1d032124ab6f2703d31ab90 Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov at redhat.com>
Date: Fri, 8 Aug 2025 10:06:19 +0200
Subject: [PATCH] [SystemZ] Remove incorrect areInlineCompatible hook (#152494)

This reverts https://github.com/llvm/llvm-project/pull/132976.

The PR incorrectly claimed that this makes inlining more liberal,
referencing the string comparison in TargetTransformInfoImpl.h.

However, the implementation that actually applies is the one in
BasicTTIImpl.h, which performs a feature subset comparison. As such,
this regressed inlining, most concerningly of functions without +vector
into functions with +vector.

Revert the change to restore the previous behavior.

(cherry picked from commit 18e4f775c33af123772409ffde69dd424b98814a)
---
 .../SystemZ/SystemZTargetTransformInfo.cpp     | 14 --------------
 .../SystemZ/SystemZTargetTransformInfo.h       |  3 ---
 .../Inline/SystemZ/inline-target-attr.ll       | 18 +++++++++---------
 3 files changed, 9 insertions(+), 26 deletions(-)

diff --git a/llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp b/llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp
index f32c9bd2bdea1..2611c291abaa6 100644
--- a/llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp
@@ -436,20 +436,6 @@ bool SystemZTTIImpl::isLSRCostLess(
              C2.ScaleCost, C2.SetupCost);
 }
 
-bool SystemZTTIImpl::areInlineCompatible(const Function *Caller,
-                                         const Function *Callee) const {
-  const TargetMachine &TM = getTLI()->getTargetMachine();
-
-  const FeatureBitset &CallerBits =
-      TM.getSubtargetImpl(*Caller)->getFeatureBits();
-  const FeatureBitset &CalleeBits =
-      TM.getSubtargetImpl(*Callee)->getFeatureBits();
-
-  // Support only equal feature bitsets. Restriction should be relaxed in the
-  // future to allow inlining when callee's bits are subset of the caller's.
-  return CallerBits == CalleeBits;
-}
-
 unsigned SystemZTTIImpl::getNumberOfRegisters(unsigned ClassID) const {
   bool Vector = (ClassID == 1);
   if (!Vector)
diff --git a/llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.h b/llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.h
index dc5736e8af009..fc681dec1859a 100644
--- a/llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.h
+++ b/llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.h
@@ -65,9 +65,6 @@ class SystemZTTIImpl final : public BasicTTIImplBase<SystemZTTIImpl> {
   bool isLSRCostLess(const TargetTransformInfo::LSRCost &C1,
                      const TargetTransformInfo::LSRCost &C2) const override;
 
-  bool areInlineCompatible(const Function *Caller,
-                           const Function *Callee) const override;
-
   /// @}
 
   /// \name Vector TTI Implementations
diff --git a/llvm/test/Transforms/Inline/SystemZ/inline-target-attr.ll b/llvm/test/Transforms/Inline/SystemZ/inline-target-attr.ll
index b5c4f42655bb4..71b463b2d2b00 100644
--- a/llvm/test/Transforms/Inline/SystemZ/inline-target-attr.ll
+++ b/llvm/test/Transforms/Inline/SystemZ/inline-target-attr.ll
@@ -12,28 +12,28 @@ entry:
 
 declare i32 @baz(...) #0
 
-define i32 @bar() #1 {
+define i32 @features_subset() #1 {
 entry:
   %call = call i32 @foo()
   ret i32 %call
-; CHECK-LABEL: bar
-; CHECK: call i32 @foo()
+; CHECK-LABEL: features_subset
+; CHECK: call i32 (...) @baz()
 }
 
-define i32 @qux() #0 {
+define i32 @features_equal() #0 {
 entry:
   %call = call i32 @foo()
   ret i32 %call
-; CHECK-LABEL: qux
+; CHECK-LABEL: features_equal
 ; CHECK: call i32 (...) @baz()
 }
 
-define i32 @quux() #2 {
+define i32 @features_different() #2 {
 entry:
-  %call = call i32 @bar()
+  %call = call i32 @foo()
   ret i32 %call
-; CHECK-LABEL: quux
-; CHECK: call i32 @bar()
+; CHECK-LABEL: features_different
+; CHECK: call i32 @foo()
 }