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| -rw-r--r-- | lib/Target/README.txt | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/lib/Target/README.txt b/lib/Target/README.txt index 9ecd2ff..a9afffd 100644 --- a/lib/Target/README.txt +++ b/lib/Target/README.txt @@ -2249,3 +2249,27 @@ S is only 6 bytes, but each element is 8 byte-aligned. We generate a loop and a memset. //===---------------------------------------------------------------------===// + +clang -O3 currently compiles this code: + +extern const int magic; +double f() { return 0.0 * magic; } + +into + +@magic = external constant i32 + +define double @_Z1fv() nounwind readnone { +entry: + %tmp = load i32* @magic, align 4, !tbaa !0 + %conv = sitofp i32 %tmp to double + %mul = fmul double %conv, 0.000000e+00 + ret double %mul +} + +We should be able to fold away this fmul to a constant, there is no 32-bit +integer which after sitofp will generate a NaN, inf, or -0.0. We should fold +this whenever the floating point type has enough exponent bits to represent +the largest integer value as < inf. + +//===---------------------------------------------------------------------===// |