[PPC] Disable rop-protect for 32-bit OS targets. (#139619)

The instructions are not supported on either 32-bit ELF (due to no
redzone) or 32-bit AIX due to the instructions always using the full
64-bit width of the register inputs.

Author: mandlebug

clang/lib/Basic/Targets/PPC.cpp

@@ -679,11 +679,17 @@ bool PPCTargetInfo::initFeatureMap(
     }
   }
 
-  if (!(ArchDefs & ArchDefinePwr8) &&
-      llvm::is_contained(FeaturesVec, "+rop-protect")) {
-    // We can turn on ROP Protect on Power 8 and above.
-    Diags.Report(diag::err_opt_not_valid_with_opt) << "-mrop-protect" << CPU;
-    return false;
+  if (llvm::is_contained(FeaturesVec, "+rop-protect")) {
+    if (PointerWidth == 32) {
+      Diags.Report(diag::err_opt_not_valid_on_target) << "-mrop-protect";
+      return false;
+    }
+
+    if (!(ArchDefs & ArchDefinePwr8)) {
+      // We can turn on ROP Protect on Power 8 and above.
+      Diags.Report(diag::err_opt_not_valid_with_opt) << "-mrop-protect" << CPU;
+      return false;
+    }
   }
 
   if (!(ArchDefs & ArchDefinePwr8) &&

clang/test/Driver/ppc-mrop-protection-support-check.c

@@ -16,6 +16,11 @@
 // RUN: not %clang -target powerpc64le-unknown-linux-gnu -fsyntax-only \
 // RUN:   -mcpu=power7 -mrop-protect %s 2>&1 | FileCheck %s --check-prefix=NOROP
 
+// RUN: not %clang -target powerpc-unknown-linux -fsyntax-only \
+// RUN: -mcpu=pwr8 -mrop-protect %s 2>&1 | FileCheck %s --check-prefix=32BIT
+// RUN: not %clang -target powerpc-unknown-aix -fsyntax-only \
+// RUN: -mcpu=pwr8 -mrop-protect %s 2>&1 | FileCheck %s --check-prefix=32BIT
+
 #ifdef __ROP_PROTECT__
 static_assert(false, "ROP Protect enabled");
 #endif
@@ -24,3 +29,4 @@ static_assert(false, "ROP Protect enabled");
 // HASROP-NOT: option '-mrop-protect' cannot be specified with
 // NOROP: option '-mrop-protect' cannot be specified with
 
+// 32BIT: option '-mrop-protect' cannot be specified on this target