From fde69dcd80cc1ca548300702adf01eeb25441f3e Mon Sep 17 00:00:00 2001
From: Steven Perron <stevenperron@google.com>
Date: Wed, 20 Feb 2019 20:05:08 -0500
Subject: [PATCH] Fix OpDot folding of half float vectors. (#2411)

* Fix OpDot folding of half float vectors.

The code that folds OpDot does not handle half floats correctly.  After
trying to multiple the first components, we get a nullptr because we
don't fold half float values.  This nullptr gets passed to the code that
does the addition, and causes an assert.

Fixes #2405.
---
 source/opt/const_folding_rules.cpp |  6 +++++-
 test/opt/fold_test.cpp             | 26 ++++++++++++++++++++++----
 2 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/source/opt/const_folding_rules.cpp b/source/opt/const_folding_rules.cpp
index f6013a3d7..3df5a83ec 100644
--- a/source/opt/const_folding_rules.cpp
+++ b/source/opt/const_folding_rules.cpp
@@ -582,13 +582,17 @@ ConstantFoldingRule FoldOpDotWithConstants() {
     std::vector<uint32_t> words = result.GetWords();
     const analysis::Constant* result_const =
         const_mgr->GetConstant(float_type, words);
-    for (uint32_t i = 0; i < a_components.size(); ++i) {
+    for (uint32_t i = 0; i < a_components.size() && result_const != nullptr;
+         ++i) {
       if (a_components[i] == nullptr || b_components[i] == nullptr) {
         return nullptr;
       }
 
       const analysis::Constant* component = FOLD_FPARITH_OP(*)(
           new_type, a_components[i], b_components[i], const_mgr);
+      if (component == nullptr) {
+        return nullptr;
+      }
       result_const =
           FOLD_FPARITH_OP(+)(new_type, result_const, component, const_mgr);
     }
diff --git a/test/opt/fold_test.cpp b/test/opt/fold_test.cpp
index d874953af..b3c344115 100644
--- a/test/opt/fold_test.cpp
+++ b/test/opt/fold_test.cpp
@@ -142,6 +142,7 @@ OpName %main "main"
 %v4double = OpTypeVector %double 4
 %v2float = OpTypeVector %float 2
 %v2double = OpTypeVector %double 2
+%v2half = OpTypeVector %half 2
 %v2bool = OpTypeVector %bool 2
 %struct_v2int_int_int = OpTypeStruct %v2int %int %int
 %_ptr_int = OpTypePointer Function %int
@@ -231,6 +232,7 @@ OpName %main "main"
 %v2double_null = OpConstantNull %v2double
 %108 = OpConstant %half 0
 %half_1 = OpConstant %half 1
+%half_0_1 = OpConstantComposite %v2half %108 %half_1
 %106 = OpConstantComposite %v4float %float_0 %float_0 %float_0 %float_0
 %v4float_0_0_0_0 = OpConstantComposite %v4float %float_0 %float_0 %float_0 %float_0
 %v4float_0_0_0_1 = OpConstantComposite %v4float %float_0 %float_0 %float_0 %float_1
@@ -3171,7 +3173,7 @@ INSTANTIATE_TEST_SUITE_P(FloatRedundantFoldingTest, GeneralInstructionFoldingTes
             "OpReturn\n" +
             "OpFunctionEnd",
         3, 2),
-    // Test case 15: Fold vector fsub with null
+    // Test case 17: Fold vector fsub with null
     InstructionFoldingCase<uint32_t>(
         Header() + "%main = OpFunction %void None %void_func\n" +
             "%main_lab = OpLabel\n" +
@@ -3181,7 +3183,7 @@ INSTANTIATE_TEST_SUITE_P(FloatRedundantFoldingTest, GeneralInstructionFoldingTes
             "OpReturn\n" +
             "OpFunctionEnd",
         3, 2),
-    // Test case 16: Fold 0.0(half) * n
+    // Test case 18: Fold 0.0(half) * n
     InstructionFoldingCase<uint32_t>(
         Header() + "%main = OpFunction %void None %void_func\n" +
             "%main_lab = OpLabel\n" +
@@ -3191,7 +3193,7 @@ INSTANTIATE_TEST_SUITE_P(FloatRedundantFoldingTest, GeneralInstructionFoldingTes
             "OpReturn\n" +
             "OpFunctionEnd",
         2, HALF_0_ID),
-    // Test case 17: Don't fold 1.0(half) * n
+    // Test case 19: Don't fold 1.0(half) * n
     InstructionFoldingCase<uint32_t>(
         Header() + "%main = OpFunction %void None %void_func\n" +
             "%main_lab = OpLabel\n" +
@@ -3201,13 +3203,29 @@ INSTANTIATE_TEST_SUITE_P(FloatRedundantFoldingTest, GeneralInstructionFoldingTes
             "OpReturn\n" +
             "OpFunctionEnd",
         2, 0),
-    // Test case 18: Don't fold 1.0 * 1.0 (half)
+    // Test case 20: Don't fold 1.0 * 1.0 (half)
     InstructionFoldingCase<uint32_t>(
         Header() + "%main = OpFunction %void None %void_func\n" +
             "%main_lab = OpLabel\n" +
             "%2 = OpFMul %half %half_1 %half_1\n" +
             "OpReturn\n" +
             "OpFunctionEnd",
+        2, 0),
+    // Test case 21: Don't fold (0.0, 1.0) * (0.0, 1.0) (half)
+    InstructionFoldingCase<uint32_t>(
+        Header() + "%main = OpFunction %void None %void_func\n" +
+            "%main_lab = OpLabel\n" +
+            "%2 = OpFMul %v2half %half_0_1 %half_0_1\n" +
+            "OpReturn\n" +
+            "OpFunctionEnd",
+        2, 0),
+    // Test case 22: Don't fold (0.0, 1.0) dotp (0.0, 1.0) (half)
+    InstructionFoldingCase<uint32_t>(
+        Header() + "%main = OpFunction %void None %void_func\n" +
+            "%main_lab = OpLabel\n" +
+            "%2 = OpDot %half %half_0_1 %half_0_1\n" +
+            "OpReturn\n" +
+            "OpFunctionEnd",
         2, 0)
 ));