spirv-diff: Fix asserts in ComparePreambleInstructions() (#4872)

These asserts are not valid for string literals, which may
contain several words:
  assert(a_operand.words.size() == 1);
  assert(b_operand.words.size() == 1);

It looks like they only make sense for the default case, which
assumes that both operands contain a single word.

Running a debug version of spirv-diff on any shader containing
a string literal will hit the original asserts.

1 files changed, 3 insertions, 3 deletions

diff --git a/source/diff/diff.cpp b/source/diff/diff.cpp
index bca31b06..17750ff2 100644
--- a/source/diff/diff.cpp
+++ b/source/diff/diff.cpp
@@ -758,9 +758,6 @@ int Differ::ComparePreambleInstructions(const opt::Instruction* a,
       return 1;
     }
 
-    assert(a_operand.words.size() == 1);
-    assert(b_operand.words.size() == 1);
-
     switch (a_operand.type) {
       case SPV_OPERAND_TYPE_ID:
         // Don't compare ids, there can't be multiple instances of the
@@ -781,6 +778,9 @@ int Differ::ComparePreambleInstructions(const opt::Instruction* a,
       }
       default:
         // Expect literal values to match.
+        assert(a_operand.words.size() == 1);
+        assert(b_operand.words.size() == 1);
+
         if (a_operand.words[0] < b_operand.words[0]) {
           return -1;
         }