[PPCAsmPrinter] support 'L' output template for memory operands

[nickdesaulniers]

Summary

L is meant to support the second word used by 32b calling conventions for 64b arguments.

This is required for build 32b PowerPC Linux kernels after upstream
commit 334710b1496a ("powerpc/uaccess: Implement unsafe_put_user() using 'asm goto'")

Thanks for the report from @nathanchance, and reference to GCC's
implementation from @segher.

Fixes: pr/46186
Fixes: https://github.com/ClangBuiltLinux/linux/issues/1044

[nickdesaulniers]

Looking at the GCC implementation, which refers to "preinc/predec/premodify" modes and small data operands, I can't help but think I may need to do something differently based on some method call against PPCSubtarget.

[echristo]

Comment what it is?

[nickdesaulniers]

• add source comment

[MaskRay]

llvm/test/CodeGen/PowerPC/inlineasm-output-template.ll

31

ppc64 has a different offset. Add a ppc64 test

[nickdesaulniers]

• add ppc64 test as per @MaskRay

[MaskRay]

Thanks!

llvm/test/CodeGen/PowerPC/inlineasm-output-template.ll

2

You can just write ppc64

[nickdesaulniers]

• drop unused part of triple, as per @MaskRay

[MaskRay]

Hi, you can drop Reviewers: Subscribers: Tags: and the text Summary: with the following script

arcfilter () {
        arc amend
        git log -1 --pretty=%B | awk '/Reviewers:|Subscribers:/{p=1} /Reviewed By:|Differential Revision:/{p=0} !p && !/^Summary:$/ {sub(/^Summary: /,"");print}' | git commit --amend --date=now -F -
}

Reviewed By: is considered important by some people. Please keep the tag. (I have updated my script to use --date=now (setting author date to committer date))

https://reviews.llvm.org/D80978 contains a git pre-push hook to automate this.

[nickdesaulniers]

In D81767#2094202, @MaskRay wrote:

Hi, you can drop Reviewers: Subscribers: Tags: and the text Summary: with the following script

arcfilter () {
        arc amend
        git log -1 --pretty=%B | awk '/Reviewers:|Subscribers:/{p=1} /Reviewed By:|Differential Revision:/{p=0} !p && !/^Summary:$/ {sub(/^Summary: /,"");print}' | git commit --amend --date=now -F -
}

Reviewed By: is considered important by some people. Please keep the tag. (I have updated my script to use --date=now (setting author date to committer date))

I've just been using arc patch to patch in the patch w/ preformatted commit, then merging that. If I don't need all that, I'll just avoid arc patch in the first place.

https://reviews.llvm.org/D80978 contains a git pre-push hook to automate this.

llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp

 bool PPCAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
                                           const char *ExtraCode,
                                           raw_ostream &O) {
   if (ExtraCode && ExtraCode[0]) {
     if (ExtraCode[1] != 0) return true; // Unknown modifier.
 
     switch (ExtraCode[0]) {
     default: return true;  // Unknown modifier.
-    case 'y': {            // A memory reference for an X-form instruction
+    case 'L': // A memory reference to the upper word of a double word op.
+      O << getDataLayout().getPointerSize() << "(";
+      printOperand(MI, OpNo, O);
+      O << ")";
+      return false;
+    case 'y': // A memory reference for an X-form instruction
       O << "0, ";
       printOperand(MI, OpNo, O);
       return false;
-    }
     case 'U': // Print 'u' for update form.
     case 'X': // Print 'x' for indexed form.
-    {
       // FIXME: Currently for PowerPC memory operands are always loaded
       // into a register, so we never get an update or indexed form.
       // This is bad even for offset forms, since even if we know we
       // have a value in -16(r1), we will generate a load into r<n>
       // and then load from 0(r<n>).  Until that issue is fixed,
       // tolerate 'U' and 'X' but don't output anything.
       assert(MI->getOperand(OpNo).isReg());
       return false;
     }
-    }
-  }
 
   assert(MI->getOperand(OpNo).isReg());
   O << "0(";
   printOperand(MI, OpNo, O);
   O << ")";
   return false;
 }
 

llvm/test/CodeGen/PowerPC/inlineasm-output-template.ll

-; RUN: llc -mtriple=ppc32-- < %s | FileCheck %s
+; RUN: llc -mtriple=ppc32 < %s | FileCheck %s
+; RUN: llc -mtriple=ppc64 < %s | FileCheck %s --check-prefix=PPC64
 
 ; Test that %c works with immediates
 ; CHECK-LABEL: test_inlineasm_c_output_template0
 ; CHECK: #TEST 42
 define dso_local i32 @test_inlineasm_c_output_template0() {
   tail call void asm sideeffect "#TEST ${0:c}", "i"(i32 42)
   ret i32 42
 }

 
 ; Test that %n works with immediates
 ; CHECK-LABEL: test_inlineasm_c_output_template2
 ; CHECK: #TEST -42
 define dso_local i32 @test_inlineasm_c_output_template2() {
   tail call void asm sideeffect "#TEST ${0:n}", "i"(i32 42)
   ret i32 42
 }
+
+; Test that the machine specific %L works with memory operands.
+; CHECK-LABEL: test_inlineasm_L_output_template
+; CHECK: # 4(5)
+; PPC64-LABEL: test_inlineasm_L_output_template
+; PPC64: # 8(4)
+define dso_local void @test_inlineasm_L_output_template(i64 %0, i64* %1) {
+  tail call void asm sideeffect "# ${0:L}", "*m"(i64* %1)
+  ret void
+}