[llvm] [SystemZ] Remove incorrect areInlineCompatible hook (PR #152494)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Nikita Popov (nikic)

<details>
<summary>Changes</summary>

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.

---
Full diff: https://github.com/llvm/llvm-project/pull/152494.diff


3 Files Affected:

- (modified) llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp (-14) 
- (modified) llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.h (-3) 
- (modified) llvm/test/Transforms/Inline/SystemZ/inline-target-attr.ll (+9-9) 


``````````diff
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()
 }
 
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/152494