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[OptimizeInstructions] Remove redundant sign-exts - #9324
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Relax isSignExted to check signExtBits <= bits, teach getSignExtBits about signed narrow loads and i64.extend_i32_s, remove unary sign-extensions when maxBits < bits, strip wider inner sign-extensions inside narrower outer ones, and fold i64.extend32_s(i64.extend_i32_u(x)) to i64.extend_i32_s(x).
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This pull request enhances sign-extension optimizations in the OptimizeInstructions pass. It introduces a helper method getExpressionSignExtBits to track sign-extension widths, optimizes nested and redundant sign-extensions (both shift-based and unary), and simplifies expressions where the input's maximum bits are already within the target sign-extend limit. The feedback suggests a minor code cleanup to avoid a redundant cast by utilizing an already-bound pointer variable.
aheejin
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Nov 1, 2026
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It would be easier to understand to have each if case comment in the code has a simple example attached to it.
Merge OptimizeInstructions::getSignExtBits into Properties::getSignExtBits using an optional LocalInfoProvider (following Bits::getMaxBits), and rename the sign/zero-extension bit width helpers from get*ExtBits to get*ExtKeptBits to clarify that they return the number of low bits kept before extension rather than the number of extended sign/zero bits.
# Conflicts: # src/passes/OptimizeInstructions.cpp
Merge OptimizeInstructions::getSignExtBits into Properties::getSignExtBits using an optional LocalInfoProvider (following Bits::getMaxBits), and rename the sign/zero-extension bit width helpers from get*ExtBits to get*ExtKeptBits to clarify that they return the number of low bits kept before extension rather than the number of extended sign/zero bits.
# Conflicts: # src/ir/properties.h # src/passes/OptimizeInstructions.cpp
…t-sign-ext # Conflicts: # src/ir/bits.h # src/ir/properties.h # src/passes/OptimizeInstructions.cpp # src/passes/PickLoadSigns.cpp
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…t-sign-ext # Conflicts: # src/ir/bits.h
aheejin
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Nov 9, 2026
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Relax isSignExted to check signExtBits <= bits, teach getSignExtBits about signed narrow loads and i64.extend_i32_s, remove unary sign-extensions when maxBits < bits, strip wider inner sign-extensions inside narrower outer ones, and fold i64.extend32_s(i64.extend_i32_u(x)) to i64.extend_i32_s(x).