[clang] [clang][Interp] Implement __builtin_ffs (PR #72988)

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Timm =?utf-8?q?Bäder?= <tbaeder at redhat.com>
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In-Reply-To: <llvm.org/llvm/llvm-project/pull/72988 at github.com>


llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Timm Baeder (tbaederr)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/72988.diff


2 Files Affected:

- (modified) clang/lib/AST/Interp/InterpBuiltin.cpp (+67) 
- (modified) clang/test/AST/Interp/builtin-functions.cpp (+24) 


``````````diff
diff --git a/clang/lib/AST/Interp/InterpBuiltin.cpp b/clang/lib/AST/Interp/InterpBuiltin.cpp
index 9cf206ecc212adb..d8802f6400071e0 100644
--- a/clang/lib/AST/Interp/InterpBuiltin.cpp
+++ b/clang/lib/AST/Interp/InterpBuiltin.cpp
@@ -533,6 +533,40 @@ static bool interp__builtin_classify_type(InterpState &S, CodePtr OpPC,
   return true;
 }
 
+/// rotateleft(value, amount)
+static bool interp__builtin_rotate(InterpState &S, CodePtr OpPC,
+                                   const InterpFrame *Frame,
+                                   const Function *Func, const CallExpr *Call,
+                                   bool Right) {
+  PrimType ArgT = *S.getContext().classify(Call->getArg(0)->getType());
+  assert(ArgT == *S.getContext().classify(Call->getArg(1)->getType()));
+
+  APSInt Amount = peekToAPSInt(S.Stk, ArgT);
+  APSInt Value = peekToAPSInt(S.Stk, ArgT, align(primSize(ArgT)) * 2);
+
+  APSInt Result;
+  if (Right)
+    Result = APSInt(Value.rotr(Amount.urem(Value.getBitWidth())),
+                    /*IsUnsigned=*/true);
+  else // Left.
+    Result = APSInt(Value.rotl(Amount.urem(Value.getBitWidth())),
+                    /*IsUnsigned=*/true);
+
+  pushAPSInt(S, Result);
+  return true;
+}
+
+static bool interp__builtin_ffs(InterpState &S, CodePtr OpPC,
+                                const InterpFrame *Frame, const Function *Func,
+                                const CallExpr *Call) {
+  PrimType ArgT = *S.getContext().classify(Call->getArg(0)->getType());
+  APSInt Value = peekToAPSInt(S.Stk, ArgT);
+
+  uint64_t N = Value.countr_zero();
+  pushInt(S, N == Value.getBitWidth() ? 0 : N + 1);
+  return true;
+}
+
 bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const Function *F,
                       const CallExpr *Call) {
   InterpFrame *Frame = S.Current;
@@ -702,6 +736,39 @@ bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const Function *F,
       return false;
     break;
 
+  case Builtin::BI__builtin_rotateleft8:
+  case Builtin::BI__builtin_rotateleft16:
+  case Builtin::BI__builtin_rotateleft32:
+  case Builtin::BI__builtin_rotateleft64:
+  case Builtin::BI_rotl8: // Microsoft variants of rotate right
+  case Builtin::BI_rotl16:
+  case Builtin::BI_rotl:
+  case Builtin::BI_lrotl:
+  case Builtin::BI_rotl64:
+    if (!interp__builtin_rotate(S, OpPC, Frame, F, Call, /*Right=*/false))
+      return false;
+    break;
+
+  case Builtin::BI__builtin_rotateright8:
+  case Builtin::BI__builtin_rotateright16:
+  case Builtin::BI__builtin_rotateright32:
+  case Builtin::BI__builtin_rotateright64:
+  case Builtin::BI_rotr8: // Microsoft variants of rotate right
+  case Builtin::BI_rotr16:
+  case Builtin::BI_rotr:
+  case Builtin::BI_lrotr:
+  case Builtin::BI_rotr64:
+    if (!interp__builtin_rotate(S, OpPC, Frame, F, Call, /*Right=*/true))
+      return false;
+    break;
+
+  case Builtin::BI__builtin_ffs:
+  case Builtin::BI__builtin_ffsl:
+  case Builtin::BI__builtin_ffsll:
+    if (!interp__builtin_ffs(S, OpPC, Frame, F, Call))
+      return false;
+    break;
+
   default:
     return false;
   }
diff --git a/clang/test/AST/Interp/builtin-functions.cpp b/clang/test/AST/Interp/builtin-functions.cpp
index 0726dab37cb4eb0..b418741f1bdcf57 100644
--- a/clang/test/AST/Interp/builtin-functions.cpp
+++ b/clang/test/AST/Interp/builtin-functions.cpp
@@ -331,3 +331,27 @@ namespace bitreverse {
   char bitreverse3[__builtin_bitreverse32(0x12345678) == 0x1E6A2C48 ? 1 : -1];
   char bitreverse4[__builtin_bitreverse64(0x0123456789ABCDEFULL) == 0xF7B3D591E6A2C480 ? 1 : -1];
 }
+
+namespace rotateleft {
+  char rotateleft1[__builtin_rotateleft8(0x01, 5) == 0x20 ? 1 : -1];
+  char rotateleft2[__builtin_rotateleft16(0x3210, 11) == 0x8190 ? 1 : -1];
+  char rotateleft3[__builtin_rotateleft32(0x76543210, 22) == 0x841D950C ? 1 : -1];
+  char rotateleft4[__builtin_rotateleft64(0xFEDCBA9876543210ULL, 55) == 0x87F6E5D4C3B2A19ULL ? 1 : -1];
+}
+
+namespace rotateright {
+  char rotateright1[__builtin_rotateright8(0x01, 5) == 0x08 ? 1 : -1];
+  char rotateright2[__builtin_rotateright16(0x3210, 11) == 0x4206 ? 1 : -1];
+  char rotateright3[__builtin_rotateright32(0x76543210, 22) == 0x50C841D9 ? 1 : -1];
+  char rotateright4[__builtin_rotateright64(0xFEDCBA9876543210ULL, 55) == 0xB97530ECA86421FDULL ? 1 : -1];
+}
+
+namespace ffs {
+  char ffs1[__builtin_ffs(0) == 0 ? 1 : -1];
+  char ffs2[__builtin_ffs(1) == 1 ? 1 : -1];
+  char ffs3[__builtin_ffs(0xfbe71) == 1 ? 1 : -1];
+  char ffs4[__builtin_ffs(0xfbe70) == 5 ? 1 : -1];
+  char ffs5[__builtin_ffs(1U << (BITSIZE(int) - 1)) == BITSIZE(int) ? 1 : -1];
+  char ffs6[__builtin_ffsl(0x10L) == 5 ? 1 : -1];
+  char ffs7[__builtin_ffsll(0x100LL) == 9 ? 1 : -1];
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/72988