[PowerPC] Treat 'Z' inline asm constraint as a true memory constraint

We currently emit incorrect codegen for this constraint because we set it as a
constraint that allows registers. This will cause the value to be copied to the
stack and that address to be passed as the address. This is not what we want.

Fixes: https://bugs.llvm.org/show_bug.cgi?id=42762

Differential revision: https://reviews.llvm.org/D77542

(cherry picked from commit aede24ecaa08db806fb173faf2de9cff95df8cee)

2 files changed, 15 insertions, 1 deletions

diff --git a/clang/lib/Basic/Targets/PPC.h b/clang/lib/Basic/Targets/PPC.h
index 270aa7ff918..ef5c2264a0b 100644
--- a/clang/lib/Basic/Targets/PPC.h
+++ b/clang/lib/Basic/Targets/PPC.h
@@ -276,11 +276,12 @@ public:
       break;
     case 'Q': // Memory operand that is an offset from a register (it is
               // usually better to use `m' or `es' in asm statements)
+      Info.setAllowsRegister();
+      LLVM_FALLTHROUGH;
     case 'Z': // Memory operand that is an indexed or indirect from a
               // register (it is usually better to use `m' or `es' in
               // asm statements)
       Info.setAllowsMemory();
-      Info.setAllowsRegister();
       break;
     case 'R': // AIX TOC entry
     case 'a': // Address operand that is an indexed or indirect from a
diff --git a/clang/test/CodeGen/ppc64-inline-asm.c b/clang/test/CodeGen/ppc64-inline-asm.c
index 3e958c328f9..0b32d0bf482 100644
--- a/clang/test/CodeGen/ppc64-inline-asm.c
+++ b/clang/test/CodeGen/ppc64-inline-asm.c
@@ -37,3 +37,16 @@ double test_fmax(double x, double y) {
 // CHECK-LABEL: double @test_fmax(double %x, double %y)
 // CHECK: call double asm "xsmaxdp ${0:x}, ${1:x}, ${2:x}", "=^ws,^ws,^ws"(double %x, double %y)
 }
+
+void testZ(void *addr) {
+  asm volatile ("dcbz %y0\n" :: "Z"(*(unsigned char *)addr) : "memory");
+// CHECK-LABEL: void @testZ(i8* %addr)
+// CHECK: call void asm sideeffect "dcbz ${0:y}\0A", "*Z,~{memory}"(i8* %addr)
+}
+
+void testZwOff(void *addr, long long off) {
+  asm volatile ("dcbz %y0\n" :: "Z"(*(unsigned char *)(addr + off)) : "memory");
+// CHECK-LABEL: void @testZwOff(i8* %addr, i64 %off)
+// CHECK: %[[VAL:[^ ]+]] = getelementptr i8, i8* %addr, i64 %off
+// CHECK: call void asm sideeffect "dcbz ${0:y}\0A", "*Z,~{memory}"(i8* %[[VAL]])
+}