5f87957fef
Testing the shift-exponent check with small width _BitInt values exposed a bug in ScalarExprEmitter::GetWidthMinusOneValue when using the result to determine valid exponent sizes. False positives were reported for some left shifts when width(LHS)-1 > range(RHS) and false negatives were reported for right shifts when value(RHS) > range(LHS). This patch caps the maximum value of GetWidthMinusOneValue to fit within range(RHS) to fix the issue with left shifts and fixes a code generation in EmitShr to fix the issue with right shifts and renames the function to GetMaximumShiftAmount to better reflect the new behaviour. Fixes #80135. Co-authored-by: Adam Magier <adam.magier@ericsson.com>
37 lines
1.5 KiB
C
37 lines
1.5 KiB
C
// RUN: %clang_cc1 %s -O0 -fsanitize=shift-exponent -emit-llvm -std=c2x -triple=x86_64-unknown-linux -o - | FileCheck %s
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// Checking that the code generation is using the unextended/untruncated
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// exponent values and capping the values accordingly
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// CHECK-LABEL: define{{.*}} i32 @test_left_variable
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int test_left_variable(unsigned _BitInt(5) b, unsigned _BitInt(2) e) {
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// CHECK: [[E_REG:%.+]] = load [[E_SIZE:i2]]
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// CHECK: icmp ule [[E_SIZE]] [[E_REG]], -1
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return b << e;
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}
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// CHECK-LABEL: define{{.*}} i32 @test_right_variable
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int test_right_variable(unsigned _BitInt(2) b, unsigned _BitInt(3) e) {
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// CHECK: [[E_REG:%.+]] = load [[E_SIZE:i3]]
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// CHECK: icmp ule [[E_SIZE]] [[E_REG]], 1
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return b >> e;
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}
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// Old code generation would give false positives on left shifts when:
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// value(e) > (width(b) - 1 % 2 ** width(e))
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// CHECK-LABEL: define{{.*}} i32 @test_left_literal
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int test_left_literal(unsigned _BitInt(5) b) {
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// CHECK-NOT: br i1 false, label %cont, label %handler.shift_out_of_bounds
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// CHECK: br i1 true, label %cont, label %handler.shift_out_of_bounds
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return b << 3uwb;
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}
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// Old code generation would give false positives on right shifts when:
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// (value(e) % 2 ** width(b)) < width(b)
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// CHECK-LABEL: define{{.*}} i32 @test_right_literal
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int test_right_literal(unsigned _BitInt(2) b) {
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// CHECK-NOT: br i1 true, label %cont, label %handler.shift_out_of_bounds
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// CHECK: br i1 false, label %cont, label %handler.shift_out_of_bounds
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return b >> 4uwb;
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}
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