[clang][CGStmt] emit i constraint rather than X for asm goto indirect dests

[nickdesaulniers]

Summary

As suggested in:
https://reviews.llvm.org/D114895#3177794
X will be converted to i by SelectionDAGISEL anyways.

[nickdesaulniers]

• write an actual commit message

[nickdesaulniers]

• verbatim

[nickdesaulniers]

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

8556 ↗

(On Diff #392984)

ugh, I didn't mean to post this hunk. I've been struggling with arc today. let me try to fix this.

[nickdesaulniers]

• try to update this correctly

[jyknight]

This looks reasonable to me, but I'd like to wait for a conclusion on D115409 first. (Which probably will result in rewriting the commit message, as well).

[nickdesaulniers]

• rebase onto D115688 + D115410

clang/lib/CodeGen/CGStmt.cpp

if (IsGCCAsmGoto) {
         Transfer.push_back(Dest.getBlock());
         llvm::BlockAddress *BA =
             llvm::BlockAddress::get(CurFn, Dest.getBlock());
         Args.push_back(BA);
         ArgTypes.push_back(BA->getType());
         ArgElemTypes.push_back(nullptr);
         if (!Constraints.empty())
           Constraints += ',';
-        Constraints += 'X';
+        Constraints += 'i';
       }
       Fallthrough = createBasicBlock("asm.fallthrough");
     }
   }
 
   // Append the "input" part of inout constraints last.
   for (unsigned i = 0, e = InOutArgs.size(); i != e; i++) {
     ArgTypes.push_back(InOutArgTypes[i]);

clang/test/CodeGen/asm-goto.c

 loop:
   return 0;
 label_true:
   return 1;
 }
 
 int test4(int out1, int out2) {
   // CHECK-LABEL: define{{.*}} i32 @test4(
-  // CHECK: callbr { i32, i32 } asm sideeffect "jne ${3:l}", "={si},={di},r,X,X,0,1
+  // CHECK: callbr { i32, i32 } asm sideeffect "jne ${3:l}", "={si},={di},r,i,i,0,1
   // CHECK: to label %asm.fallthrough [label %label_true, label %loop]
   // CHECK-LABEL: asm.fallthrough:
   if (out1 < out2)
     asm volatile goto("jne %l3" : "+S"(out1), "+D"(out2) : "r"(out1) :: label_true, loop);
   else
     asm volatile goto("jne %l5" : "+S"(out1), "+D"(out2) : "r"(out1), "r"(out2) :: label_true, loop);
-  // CHECK: callbr { i32, i32 } asm sideeffect "jne ${5:l}", "={si},={di},r,r,X,X,0,1
+  // CHECK: callbr { i32, i32 } asm sideeffect "jne ${5:l}", "={si},={di},r,r,i,i,0,1
   // CHECK: to label %asm.fallthrough2 [label %label_true, label %loop]
   // CHECK-LABEL: asm.fallthrough2:
   return out1 + out2;
 loop:
   return -1;
 label_true:
   return -2;
 }
 
 int test5(int addr, int size, int limit) {
   // CHECK-LABEL: define{{.*}} i32 @test5(
-  // CHECK: callbr i32 asm "add $1,$0 ; jc ${3:l} ; cmp $2,$0 ; ja ${3:l} ; ", "=r,imr,imr,X,0
+  // CHECK: callbr i32 asm "add $1,$0 ; jc ${3:l} ; cmp $2,$0 ; ja ${3:l} ; ", "=r,imr,imr,i,0
   // CHECK: to label %asm.fallthrough [label %t_err]
   // CHECK-LABEL: asm.fallthrough:
   asm goto(
       "add %1,%0 ; "
       "jc %l[t_err] ; "
       "cmp %2,%0 ; "
       "ja %l[t_err] ; "
       : "+r" (addr)
       : "g" (size), "g" (limit)
       : : t_err);
   return 0;
 t_err:
   return 1;
 }
 
 int test6(int out1) {
   // CHECK-LABEL: define{{.*}} i32 @test6(
-  // CHECK: callbr i32 asm sideeffect "testl $0, $0; testl $1, $1; jne ${2:l}", "={si},r,X,X,0,{{.*}} i8* blockaddress(@test6, %label_true), i8* blockaddress(@test6, %landing)
+  // CHECK: callbr i32 asm sideeffect "testl $0, $0; testl $1, $1; jne ${2:l}", "={si},r,i,i,0,{{.*}} i8* blockaddress(@test6, %label_true), i8* blockaddress(@test6, %landing)
   // CHECK: to label %asm.fallthrough [label %label_true, label %landing]
   // CHECK-LABEL: asm.fallthrough:
   // CHECK-LABEL: landing:
   int out2 = 42;
   asm volatile goto("testl %0, %0; testl %1, %1; jne %l2" : "+S"(out2) : "r"(out1) :: label_true, landing);
 landing:
   return out1 + out2;
 label_true:
   return -2;
 }

clang/test/CodeGen/asm.c

void t31(int len) {
   // CHECK: @t31
   // CHECK: call void asm sideeffect "", "=*%rm,=*rm,0,1,~{dirflag},~{fpsr},~{flags}"
 }
 
 // CHECK: @t32
 int t32(int cond)
 {
   asm goto("testl %0, %0; jne %l1;" :: "r"(cond)::label_true, loop);
-  // CHECK: callbr void asm sideeffect "testl $0, $0; jne ${1:l};", "r,X,X,~{dirflag},~{fpsr},~{flags}"(i32 %0, i8* blockaddress(@t32, %label_true), i8* blockaddress(@t32, %loop)) #1
+  // CHECK: callbr void asm sideeffect "testl $0, $0; jne ${1:l};", "r,i,i,~{dirflag},~{fpsr},~{flags}"(i32 %0, i8* blockaddress(@t32, %label_true), i8* blockaddress(@t32, %loop)) #1
   return 0;
 loop:
   return 0;
 label_true:
   return 1;
 }

clang/test/Modules/asm-goto.c

 // RUN: rm -rf %t
 // RUN: %clang_cc1 -fmodules -fno-implicit-modules -x c -I%S/Inputs/asm-goto -emit-module %S/Inputs/asm-goto/module.modulemap -fmodule-name=a -o %t/a.pcm
 // RUN: %clang_cc1 -fmodules -fno-implicit-modules -x c -I%S/Inputs/asm-goto -emit-llvm -o - %s -fmodule-file=%t/a.pcm | FileCheck %s
 #include "a.h"
 
 // CHECK-LABEL: define {{.*}} @foo(
-// CHECK: callbr {{.*}} "=r,X{{.*}} blockaddress(@foo, %indirect))
+// CHECK: callbr {{.*}} "=r,i{{.*}} blockaddress(@foo, %indirect))
 // CHECK-NEXT: to label %asm.fallthrough [label %indirect]
 
 int bar(void) {
   return foo();
 }