Fix precision propagation around shifts

Test/baseResults/spv.precision.frag.out

 spv.precision.frag
 // Module Version 10000
 // Generated by (magic number): 8000a
-// Id's are bound by 146
+// Id's are bound by 165
 
                               Capability Shader
                1:             ExtInstImport  "GLSL.std.450"
                               MemoryModel Logical GLSL450
-                              EntryPoint Fragment 4  "main" 23 62 64 76 119
+                              EntryPoint Fragment 4  "main" 23 62 64 76 119 149
                               ExecutionMode 4 OriginUpperLeft
                               Source ESSL 310
+                              SourceExtension  "GL_OES_sample_variables"
                               Name 4  "main"
                               Name 12  "foo(vf3;"
                               Name 11  "mv3"
@@ -33,6 +34,7 @@ spv.precision.frag
                               MemberName 117(S) 0  "a"
                               MemberName 117(S) 1  "b"
                               Name 119  "s"
+                              Name 149  "gl_SampleMaskIn"
                               Decorate 12(foo(vf3;) RelaxedPrecision
                               Decorate 11(mv3) RelaxedPrecision
                               Decorate 23(highfin) Location 2
@@ -97,6 +99,15 @@ spv.precision.frag
                               Decorate 143 RelaxedPrecision
                               Decorate 144 RelaxedPrecision
                               Decorate 145 RelaxedPrecision
+                              Decorate 149(gl_SampleMaskIn) Flat
+                              Decorate 149(gl_SampleMaskIn) BuiltIn SampleMask
+                              Decorate 153 RelaxedPrecision
+                              Decorate 156 RelaxedPrecision
+                              Decorate 159 RelaxedPrecision
+                              Decorate 160 RelaxedPrecision
+                              Decorate 162 RelaxedPrecision
+                              Decorate 163 RelaxedPrecision
+                              Decorate 164 RelaxedPrecision
                2:             TypeVoid
                3:             TypeFunction 2
                6:             TypeFloat 32
@@ -147,6 +158,11 @@ spv.precision.frag
              133:    6(float) Constant 1082549862
              138:    6(float) Constant 1073741824
              142:    6(float) Constant 1077936128
+             146:     95(int) Constant 1
+             147:             TypeArray 39(int) 146
+             148:             TypePointer Input 147
+149(gl_SampleMaskIn):    148(ptr) Variable Input
+             150:             TypePointer Input 39(int)
          4(main):           2 Function None 3
                5:             Label
          41(sum):     40(ptr) Variable Function
@@ -156,6 +172,7 @@ spv.precision.frag
  72(local_highp):     71(ptr) Variable Function
       108(param):     16(ptr) Variable Function
              135:     71(ptr) Variable Function
+             156:     71(ptr) Variable Function
               44:     39(int) Load 43(uniform_medium)
               46:     39(int) Load 45(uniform_high)
               47:     39(int) IAdd 44 46
@@ -249,6 +266,26 @@ spv.precision.frag
              137:             Label
              145:   21(fvec4) Load 135
                               Store 76(mediumfout) 145
+             151:    150(ptr) AccessChain 149(gl_SampleMaskIn) 120
+             152:     39(int) Load 151
+             153:     39(int) Load 43(uniform_medium)
+             154:     39(int) ShiftRightArithmetic 152 153
+             155:    14(bool) SGreaterThan 154 120
+                              SelectionMerge 158 None
+                              BranchConditional 155 157 161
+             157:               Label
+             159:   21(fvec4)   Load 76(mediumfout)
+             160:   21(fvec4)   VectorTimesScalar 159 138
+                                Store 156 160
+                                Branch 158
+             161:               Label
+             162:   21(fvec4)   Load 76(mediumfout)
+             163:   21(fvec4)   VectorTimesScalar 162 142
+                                Store 156 163
+                                Branch 158
+             158:             Label
+             164:   21(fvec4) Load 156
+                              Store 76(mediumfout) 164
                               Return
                               FunctionEnd
     12(foo(vf3;):    9(fvec2) Function None 10

Test/spv.precision.frag

 #version 310 es
+#extension GL_OES_sample_variables : enable
 precision mediump float;
 in lowp float lowfin;
 in mediump float mediumfin;
@@ -59,4 +60,5 @@ void main()
     mediumfout *= s.b;
 
     mediumfout = ((mediumfin * mediumfin > 4.2) ? 2.0 * mediumfout : 3.0 * mediumfout);
+    mediumfout = ((gl_SampleMaskIn[0] >> uniform_medium > 0) ? 2.0 * mediumfout : 3.0 * mediumfout);
 }

glslang/MachineIndependent/Intermediate.cpp

@@ -3776,11 +3776,16 @@ void TIntermBinary::updatePrecision()
 {
      if (getBasicType() == EbtInt || getBasicType() == EbtUint ||
          getBasicType() == EbtFloat || getBasicType() == EbtFloat16) {
-        getQualifier().precision = std::max(right->getQualifier().precision, left->getQualifier().precision);
-        if (getQualifier().precision != EpqNone) {
-            left->propagatePrecision(getQualifier().precision);
-            right->propagatePrecision(getQualifier().precision);
-        }
+       if (op == EOpRightShift || op == EOpLeftShift) {
+         // For shifts get precision from left side only and thus no need to propagate
+         getQualifier().precision = left->getQualifier().precision;
+       } else {
+         getQualifier().precision = std::max(right->getQualifier().precision, left->getQualifier().precision);
+         if (getQualifier().precision != EpqNone) {
+           left->propagatePrecision(getQualifier().precision);
+           right->propagatePrecision(getQualifier().precision);
+         }
+       }
     }
 }