[clang] [llvm] PowerPC: Support `Q` constraint and `P` modifier in Inline Asm (PR #163616)

[via cfe-commits]

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+// RUN: %clang_cc1 -emit-llvm -triple powerpc64-ibm-aix-xcoff \
+// RUN:   %s -o - | FileCheck %s
+
+#include <stdint.h>
+
+// Test Atomic Memory Operation Support:
+// This test case takes an address and performs an atomic load at that address.
+// The purpose is to test the Q machine constraint and P machine constraint
+// argument modifier together.
+// These constraints on the pointer `ptr` read as: constrain (uint32_t*)ptr to
+// read and writeable X-Form Addressed Memory operands.
+static __attribute__((noinline))
+uint32_t atomic_load(uint32_t *ptr, uint32_t val)
+{
+// CHECK-LABEL: define{{.*}} i32 @atomic_load(ptr noundef %ptr, i32 noundef zeroext %val)
+// CHECK:  %3 = call { i128, i32 } asm sideeffect "mr ${1:L},$3\0A\09 lwat $1,${0:P},$4\0A\09 mr $2,$1\0A", "=*Q,=&r,=r,r,n,0"(ptr elementtype(i32) %arrayidx, i32 %2, i32 0, i32 %1)
+  unsigned __int128 tmp;
+  uint32_t ret;
+  __asm__ volatile ("mr %L1,%3\n"
+                    "\t lwat %1,%P0,%4\n"
+                    "\t mr %2,%1\n"
+                    : "+Q" (ptr[0]), "=&r" (tmp), "=r" (ret)
+                    : "r" (val), "n" (0x00));
+  return ret;
+}
+
+int main(int argc, char **argv) {
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RolandF77 wrote:

Given what the checks are, main seems not needed.

https://github.com/llvm/llvm-project/pull/163616