; ModuleID = 'new.o' target datalayout = "e-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-p:32:32:32-v128:32:128-n32-S128" target triple = "asmjs-unknown-emscripten" declare i32 @printf(i8* noalias, ...) nounwind @x = common global [4194304 x i8] zeroinitializer, align 4 @.str = private constant [6 x i8] c"*%d*\0A\00", align 1 define i8* @test_gep(i32 %y) nounwind readnone { ; JavaScript uses double precision 64-bit floating point values, with ; a 53 bit mantissa. The maximum precisely representable integer is ; 9007199254740992. A number close to that limit is constructed here ; for the constant part of the getelementptr instruction: ; 4194304 * 2147483647 == 9007199250546688 == 9007199254740992 - 4194304 ; If that number appears in JavaScript source instead of being properly ; limited to 32 bits, the %y parameter can be used to exceed the maximum ; precisely representable integer, and make the computation inexact. %test_res = getelementptr [4194304 x i8]* @x, i32 2147483647, i32 %y ret i8* %test_res } define i32 @main() { %res_0 = call i8* (i32)* @test_gep(i32 1000000000) %res_1 = call i8* (i32)* @test_gep(i32 1000000001) %res_0_i = ptrtoint i8* %res_0 to i32 %res_1_i = ptrtoint i8* %res_1 to i32 ; If getelementptr limited the constant part of the offset to 32 bits, ; result will be 1. Otherwise, it cannot be 1 because the large numbers in ; the calculation cannot be accurately represented by floating point math. %res_diff = sub i32 %res_1_i, %res_0_i %printf_res = call i32 (i8*, ...)* @printf(i8* getelementptr inbounds ([6 x i8]* @.str, i32 0, i32 0), i32 %res_diff) ret i32 0 }