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Moving potential optimizations out of PR2330 into lib/Target/README.txt.
Hopefully this isn't too much stuff to dump into this file. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60285 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eli Friedman
parent
fc69cb475f
commit
4e16b29a6b
@ -1002,3 +1002,265 @@ define i8 @addshr(i8 %x) readnone nounwind {
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}
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//===---------------------------------------------------------------------===//
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From gcc bug 24696:
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int
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f (unsigned long a, unsigned long b, unsigned long c)
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{
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return ((a & (c - 1)) != 0) || ((b & (c - 1)) != 0);
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}
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int
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f (unsigned long a, unsigned long b, unsigned long c)
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{
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return ((a & (c - 1)) != 0) | ((b & (c - 1)) != 0);
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}
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Both should combine to ((a|b) & (c-1)) != 0. Currently not optimized with
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"clang -emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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From GCC Bug 20192:
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#define PMD_MASK (~((1UL << 23) - 1))
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void clear_pmd_range(unsigned long start, unsigned long end)
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{
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if (!(start & ~PMD_MASK) && !(end & ~PMD_MASK))
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f();
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}
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The expression should optimize to something like
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"!((start|end)&~PMD_MASK). Currently not optimized with "clang
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-emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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From GCC Bug 15241:
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unsigned int
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foo (unsigned int a, unsigned int b)
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{
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if (a <= 7 && b <= 7)
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baz ();
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}
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Should combine to "(a|b) <= 7". Currently not optimized with "clang
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-emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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From GCC Bug 3756:
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int
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pn (int n)
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{
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return (n >= 0 ? 1 : -1);
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}
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Should combine to (n >> 31) | 1. Currently not optimized with "clang
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-emit-llvm-bc | opt -std-compile-opts | llc".
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//===---------------------------------------------------------------------===//
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From GCC Bug 28685:
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int test(int a, int b)
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{
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int lt = a < b;
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int eq = a == b;
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return (lt || eq);
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}
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Should combine to "a <= b". Currently not optimized with "clang
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-emit-llvm-bc | opt -std-compile-opts | llc".
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//===---------------------------------------------------------------------===//
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void a(int variable)
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{
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if (variable == 4 || variable == 6)
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bar();
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}
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This should optimize to "if ((variable | 2) == 6)". Currently not
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optimized with "clang -emit-llvm-bc | opt -std-compile-opts | llc".
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//===---------------------------------------------------------------------===//
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unsigned int f(unsigned int i, unsigned int n) {++i; if (i == n) ++i; return
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i;}
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unsigned int f2(unsigned int i, unsigned int n) {++i; i += i == n; return i;}
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These should combine to the same thing. Currently, the first function
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produces better code on X86.
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//===---------------------------------------------------------------------===//
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From GCC Bug 33512:
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int f(int y, int x)
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{
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return x & ((~x) | y);
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}
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Should combine to x & y. Currently not optimized with "clang
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-emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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From GCC Bug 15784:
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#define abs(x) x>0?x:-x
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int f(int x, int y)
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{
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return (abs(x)) >= 0;
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}
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This should optimize to x == INT_MIN. (With -fwrapv.) Currently not
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optimized with "clang -emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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From GCC Bug 14753:
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void
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rotate_cst (unsigned int a)
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{
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a = (a << 10) | (a >> 22);
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if (a == 123)
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bar ();
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}
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void
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minus_cst (unsigned int a)
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{
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unsigned int tem;
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tem = 20 - a;
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if (tem == 5)
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bar ();
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}
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void
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mask_gt (unsigned int a)
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{
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/* This is equivalent to a > 15. */
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if ((a & ~7) > 8)
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bar ();
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}
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void
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rshift_gt (unsigned int a)
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{
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/* This is equivalent to a > 23. */
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if ((a >> 2) > 5)
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bar ();
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}
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All should simplify to a single comparison. All of these are
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currently not optimized with "clang -emit-llvm-bc | opt
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-std-compile-opts".
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//===---------------------------------------------------------------------===//
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From GCC Bug 32605:
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int c(int* x) {return (char*)x+2 == (char*)x;}
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Should combine to 0. Currently not optimized with "clang
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-emit-llvm-bc | opt -std-compile-opts" (although llc can optimize it).
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//===---------------------------------------------------------------------===//
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int a(unsigned char* b) {return *b > 99;}
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There's an unnecessary zext in the generated code with "clang
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-emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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int a(int a, int b) {return ((a|b)&1) | (b&-2);}
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Should be combined to "(a&1)|b". Currently not optimized with "clang
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-emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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int a(unsigned b) {return ((b << 31) | (b << 30)) >> 31;}
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Should be combined to "((b >> 1) | b) & 1". Currently not optimized
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with "clang -emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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unsigned a(unsigned x, unsigned y) { return x | (y & 1) | (y & 2);}
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Should combine to "x | (y & 3)". Currently not optimized with "clang
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-emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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unsigned a(unsigned a) {return ((a | 1) & 3) | (a & -4);}
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Should combine to "a | 1". Currently not optimized with "clang
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-emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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int a(int a, int b, int c) {return ((a&~b) | (~a&b));}
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Should fold to xor. Currently not optimized with "clang -emit-llvm-bc
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| opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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int a(int a, int b, int c) {return (~a & c) | ((c|a) & b);}
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Should fold to "(~a & c) | (a & b)". Currently not optimized with
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"clang -emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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int a(int a,int b) {return (~(a|b))|a;}
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Should fold to "a|~b". Currently not optimized with "clang
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-emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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int a(int a, int b) {return (a&&b) || (a&&!b);}
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Should fold to "a". Currently not optimized with "clang -emit-llvm-bc
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| opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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int a(int a, int b, int c) {return (a&&b) || (!a&&c);}
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Should fold to "a ? b : c", or at least something sane. Currently not
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optimized with "clang -emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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int a(int a, int b, int c) {return (a&&b) || (a&&c) || (a&&b&&c);}
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Should fold to a && (b || c). Currently not optimized with "clang
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-emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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int a(int x) {return x | ((x & 8) ^ 8);}
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Should combine to x | 8. Currently not optimized with "clang
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-emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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int a(int x) {return x ^ ((x & 8) ^ 8);}
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Should also combine to x | 8. Currently not optimized with "clang
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-emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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int a(int x) {return (x & 8) == 0 ? -1 : -9;}
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Should combine to (x | -9) ^ 8. Currently not optimized with "clang
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-emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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int a(int x) {return (x & 8) == 0 ? -9 : -1;}
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Should combine to x | -9. Currently not optimized with "clang
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-emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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int a(int x) {return ((x | -9) ^ 8) & x;}
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Should combine to x & -9. Currently not optimized with "clang
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-emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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unsigned a(unsigned a) {return a * 0x11111111 >> 28 & 1;}
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Should combine to "a * 0x88888888 >> 31". Currently not optimized
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with "clang -emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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unsigned a(char* x) {if ((*x & 32) == 0) return b();}
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There's an unnecessary zext in the generated code with "clang
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-emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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unsigned a(unsigned long long x) {return 40 * (x >> 1);}
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Should combine to "20 * (((unsigned)x) & -2)". Currently not
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optimized with "clang -emit-llvm-bc | opt -std-compile-opts".
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//===---------------------------------------------------------------------===//
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