[mlir][Transforms] Fix mapping in findOrBuildReplacementValue

[matthias-springer]

Fixes two minor issues in findOrBuildReplacementValue:

• Remove a redundant mapping.map.
• Map repl instead of value. We used to overwrite an existing mapping, which could introduce extra materializations.

Note: We generally do not want to overwrite mappings, but create a chain of mappings. There are still a few more places, where a mapping is overwritten. Once those are fixed, I will put an assertion into ConversionValueMapping::map.

[llvmbot]

@llvm/pr-subscribers-mlir-core

@llvm/pr-subscribers-mlir

Author: Matthias Springer (matthias-springer)

Changes

Fixes two minor issues in findOrBuildReplacementValue:

• Remove a redundant mapping.map.
• Map repl instead of value. We used to overwrite an existing mapping, which could introduce extra materializations.

Note: We generally do not want to overwrite mappings, but create a chain of mappings. There are still a few more places, where a mapping is overwritten. Once those are fixed, I will put an assertion into ConversionValueMapping::map.

---

Full diff: https://github.com/llvm/llvm-project/pull/121644.diff

1 Files Affected:

• (modified) mlir/lib/Transforms/Utils/DialectConversion.cpp (+1-2)

diff --git a/mlir/lib/Transforms/Utils/DialectConversion.cpp b/mlir/lib/Transforms/Utils/DialectConversion.cpp
index 6c3863e4c7f666..4904d3ce3f8635 100644
--- a/mlir/lib/Transforms/Utils/DialectConversion.cpp
+++ b/mlir/lib/Transforms/Utils/DialectConversion.cpp
@@ -1533,11 +1533,10 @@ Value ConversionPatternRewriterImpl::findOrBuildReplacementValue(
   Value castValue =
       buildUnresolvedMaterialization(MaterializationKind::Source,
                                      computeInsertPoint(repl), value.getLoc(),
-                                     /*valuesToMap=*/{value}, /*inputs=*/repl,
+                                     /*valuesToMap=*/repl, /*inputs=*/repl,
                                      /*outputType=*/value.getType(),
                                      /*originalType=*/Type(), converter)
           .front();
-  mapping.map(value, castValue);
   return castValue;
 }