[PATCH] D132141: [X86] Emulate _rdrand64_step with two rdrand32 if it is 32bit

[Bing Yu via Phabricator via cfe-commits]

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Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D132141

Files:
  clang/lib/Headers/immintrin.h
  clang/test/CodeGen/X86/rdrand-builtins.c


Index: clang/test/CodeGen/X86/rdrand-builtins.c
===================================================================
--- clang/test/CodeGen/X86/rdrand-builtins.c
+++ clang/test/CodeGen/X86/rdrand-builtins.c
@@ -1,5 +1,5 @@
 // RUN: %clang_cc1 -no-opaque-pointers -ffreestanding %s -triple=x86_64-unknown-unknown -target-feature +rdrnd -target-feature +rdseed -emit-llvm -o - -Wall -Werror | FileCheck %s --check-prefixes=CHECK,X64
-// RUN: %clang_cc1 -no-opaque-pointers -ffreestanding %s -triple=i386-unknown-unknown -target-feature +rdrnd -target-feature +rdseed -emit-llvm -o - -Wall -Werror | FileCheck %s --check-prefixes=CHECK
+// RUN: %clang_cc1 -no-opaque-pointers -ffreestanding %s -triple=i386-unknown-unknown -target-feature +rdrnd -target-feature +rdseed -emit-llvm -o - -Wall -Werror | FileCheck %s --check-prefixes=CHECK,X32
 
 #include <immintrin.h>
 
@@ -24,6 +24,29 @@
 // X64: call { i64, i32 } @llvm.x86.rdrand.64
 // X64: store i64
 }
+#else
+int rdrand64(unsigned long long *p) {
+// X32: @rdrand64
+// X32: [[RETVAL_I:%.*]] = alloca i32, align 4
+// X32: call { i32, i32 } @llvm.x86.rdrand.32
+// X32: store i32
+// X32: call { i32, i32 } @llvm.x86.rdrand.32
+// X32: store i32
+// X32: [[AND_I:%.*]] = and i32
+// X32: [[TOBOOL_I:%.*]] = icmp ne i32 [[AND_I]], 0
+// X32: br i1 [[TOBOOL_I]], label [[IF_THEN_I:%.*]], label [[IF_ELSE_I:%.*]]
+// X32: if.then.i:
+// X32: store i64
+// X32: store i32 1, i32* [[RETVAL_I]], align 4
+// X32: br label [[_RDRAND64_STEP_EXIT:%.*]]
+// X32: if.else.i:
+// X32: store i64 0
+// X32: store i32 0, i32* [[RETVAL_I]], align 4
+// X32: br label [[_RDRAND64_STEP_EXIT]]
+// X32: _rdrand64_step.exit:
+// X32: %{{.*}} = load i32, i32* [[RETVAL_I]], align 4
+  return _rdrand64_step(p);
+}
 #endif
 
 int rdseed16(unsigned short *p) {
Index: clang/lib/Headers/immintrin.h
===================================================================
--- clang/lib/Headers/immintrin.h
+++ clang/lib/Headers/immintrin.h
@@ -291,6 +291,22 @@
 {
   return (int)__builtin_ia32_rdrand64_step(__p);
 }
+#else
+// We need to emulate the functionality of 64-bit rdrand with 2 32-bit
+// rdrand instructions.
+static __inline__ int __attribute__((__always_inline__, __nodebug__, __target__("rdrnd")))
+_rdrand64_step(unsigned long long *__p)
+{
+  unsigned long long tmp;
+  if (__builtin_ia32_rdrand32_step((unsigned int *)&tmp) &
+      __builtin_ia32_rdrand32_step(((unsigned int *)&tmp) + 1)) {
+    *__p = tmp;
+    return 1;
+  } else {
+    *__p = 0;
+    return 0;
+  }
+}
 #endif
 #endif /* __RDRND__ */
 


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