Change default type for 1<<x to int.

tools/clang/include/clang/Basic/DiagnosticGroups.td

@@ -786,4 +786,5 @@ def HLSLAttributeType : DiagGroup<"attribute-type">;
 def HLSLSpecifierOverride : DiagGroup<"specifier-override">;
 def HLSLPackOffsetOverride : DiagGroup<"packoffset-override">;
 def HLSLCommaInInit : DiagGroup<"comma-in-init">;
+def HLSLAmbigLitShift : DiagGroup<"ambig-lit-shift">;
 // HLSL Change Ends

tools/clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -7624,6 +7624,9 @@ def warn_hlsl_narrowing : Warning<
 def warn_hlsl_sema_minprecision_promotion : Warning <
   "%0 is promoted to %1">,
   InGroup<Conversion>, DefaultWarn;
+def warn_hlsl_ambiguous_literal_shift : Warning <
+  "ambiguous type for bit shift; use a type suffix on literal values, like 'L' or 'U', or a cast">,
+  InGroup<HLSLAmbigLitShift>, DefaultWarn;
 def warn_hlsl_implicit_vector_truncation  : Warning<
   "implicit truncation of vector type">,
   InGroup<Conversion>, DefaultWarn;

tools/clang/lib/Sema/SemaHLSL.cpp

@@ -9104,7 +9104,11 @@ void HLSLExternalSource::CheckBinOpForHLSL(
                rightElementKind != AR_BASIC_LITERAL_INT &&
                rightElementKind != AR_BASIC_LITERAL_FLOAT) {
       // For case like 1<<x.
-      resultElementKind = AR_BASIC_UINT32;
+      m_sema->Diag(OpLoc, diag::warn_hlsl_ambiguous_literal_shift);
+      if (rightElementKind == AR_BASIC_UINT32)
+        resultElementKind = AR_BASIC_UINT32;
+      else
+        resultElementKind = AR_BASIC_INT32;
     } else if (resultElementKind == AR_BASIC_BOOL &&
                BinaryOperatorKindRequiresBoolAsNumeric(Opc)) {
       resultElementKind = AR_BASIC_INT32;

tools/clang/test/HLSL/literals.hlsl

@@ -35,6 +35,12 @@ uint64_t overload2(uint64_t v1, uint64_t v2) { return (uint64_t)700; }  /* fxc-e
 min16float m16f;
 min16float4x4 m16f4x4;
 
+
+int i;
+uint u;
+min16int m16i;
+min16uint m16u;
+
 float test() {
   // Ambiguous due to literal int and literal float:
   VERIFY_TYPES(float, overload1(1.5));                      /* expected-error {{call to 'overload1' is ambiguous}} fxc-error {{X3067: 'overload1': ambiguous function call}} */
@@ -186,5 +192,17 @@ float test() {
   VERIFY_TYPE_CONVERSION(min16int, 1UL); /* fxc-warning {{X3205: conversion from larger type to smaller, possible loss of data}} */
   VERIFY_TYPE_CONVERSION(min16int, 1LL); /* fxc-error {{X3000: syntax error: unexpected token 'L'}} */
 
+  // Type depends on LHS
+  VERIFY_TYPES(int, 1L << u);
+  VERIFY_TYPES(uint, 1U << i);
+  // FXC behavior: pick uint if RHS is uint, otherwise, pick int
+  // DXC: Warn for ambiguous literal LHS, then match FXC for type
+  VERIFY_TYPES(int, 1 << i);/* expected-warning {{ambiguous type for bit shift; use a type suffix on literal values, like 'L' or 'U', or a cast}} */
+  VERIFY_TYPES(uint, 1 << u);/* expected-warning {{ambiguous type for bit shift; use a type suffix on literal values, like 'L' or 'U', or a cast}} */
+  VERIFY_TYPES(int, 1 << m16i);/* expected-warning {{ambiguous type for bit shift; use a type suffix on literal values, like 'L' or 'U', or a cast}} */
+  VERIFY_TYPES(int, 1 << m16u);/* expected-warning {{ambiguous type for bit shift; use a type suffix on literal values, like 'L' or 'U', or a cast}} */
+
   return 0.0f;
 }
+
+int half_btf(int w,int bit) { return (w + (1<<bit)) >> bit; } /* expected-warning {{ambiguous type for bit shift; use a type suffix on literal values, like 'L' or 'U', or a cast}} */

tools/clang/test/HLSLFileCheck/hlsl/operators/binary/shr.hlsl

@@ -0,0 +1,26 @@
+// RUN: %dxc -E main -T ps_6_0 -DDEFAULT  %s | FileCheck %s -check-prefix=DEFAULT
+// RUN: %dxc -E main -T ps_6_0 -DUINT_SHIFT  %s | FileCheck %s -check-prefix=UINT
+// RUN: %dxc -E main -T ps_6_0 -DINT_SHIFT  %s | FileCheck %s -check-prefix=INT
+
+// Make sure generate ashr and lshr
+// DEFAULT:ashr
+// UINT:lshr
+// INT:ashr
+
+int i;
+
+#ifdef DEFAULT
+int half_btf(int w,int bit) { return (w + (1<<bit)) >> bit; }
+#endif
+
+#ifdef UINT_SHIFT
+int half_btf(int w,int bit) { return (w + (1U<<bit)) >> bit; }
+#endif
+
+#ifdef INT_SHIFT
+int half_btf(int w,int bit) { return (w + (1L<<bit)) >> bit; }
+#endif
+
+int main(int w:W) : SV_Target {
+  return half_btf(i,12);
+}