[llvm-exegesis] Fix 44b9942898c7.

[courbet]

Summary

Add missing stack release instructions in
loadImplicitRegAndFinalize.

[courbet]

And add unit test.

[kadircet]

LGTM, thanks!

llvm/test/tools/llvm-exegesis/X86/latency-SQRTSSr.s

2

could you add a comment about the test? I believe the context wouldn't be clear to anyone looking at the test or this revision.

[courbet]

More comments.

[pengfei]

Thanks and sorry for the mistake.

llvm/test/tools/llvm-exegesis/X86/latency-SQRTSSr.s

+# RUN: llvm-exegesis -mode=latency -opcode-name=SQRTSSr -repetition-mode=loop | FileCheck %s
+
+CHECK:      ---
+CHECK-NEXT: mode: latency
+CHECK-NEXT: key:
+CHECK-NEXT:   instructions:
+CHECK-NEXT:     SQRTSSr
+CHECK-NEXT: config: ''
+CHECK-NEXT: register_initial_values:
+CHECK-NOT: crashed
+CHECK-LAST: ...

llvm/tools/llvm-exegesis/lib/X86/Target.cpp

ConstantInliner::loadImplicitRegAndFinalize(unsigned Opcode, unsigned Value) {
   add(fillStackSpace(X86::MOV32mi, 0, Value)); // Mask all FP exceptions
   add(MCInstBuilder(Opcode)
           // Address = ESP
           .addReg(X86::RSP) // BaseReg
           .addImm(1)        // ScaleAmt
           .addReg(0)        // IndexReg
           .addImm(0)        // Disp
           .addReg(0));      // Segment
+  add(releaseStackSpace(4));
   return std::move(Instructions);
 }
 
 void ConstantInliner::initStack(unsigned Bytes) {
   assert(Constant_.getBitWidth() <= Bytes * 8 &&
          "Value does not have the correct size");
   const APInt WideConstant = Constant_.getBitWidth() < Bytes * 8
                                  ? Constant_.sext(Bytes * 8)